Thai Poached Fish in Coconut Broth (Pla Tom Kati)

Balance is everything. Thai cooking understands this in its bones — taste and adjust. This poached fish is a perfect example of that philosophy in action. Every element in this dish has a purpose. The heat wakes you up. The herbs cool you down. The fish sauce grounds everything. Together, they create harmony on the plate. Fresh herbs are life.

Ingredients

For the Fish

4 firm white fish fillets (6-8 oz each), such as sea bass, snapper, halibut, or cod

1/2 teaspoon sea salt

1/4 teaspoon white pepper

For the Coconut Poaching Broth

2 cans (13.5 oz each) full-fat coconut milk, divided

1 cup fish stock or light vegetable stock

3 stalks fresh lemongrass, bottom 4 inches only, bruised with back of knife and cut into 2-inch pieces

1 piece fresh galangal (about 3 inches), sliced into thin rounds

6 kaffir lime leaves, torn (or zest of 2 limes)

4 Thai shallots or 2 regular shallots, halved

4 cloves garlic, lightly smashed

2-3 fresh Thai bird chilies, lightly crushed (adjust to taste)

1/4 cup fresh cilantro stems

For Seasoning the Broth

3 tablespoons fish sauce, plus more to taste

1 tablespoon palm sugar or light brown sugar

2 tablespoons fresh lime juice

1/2 teaspoon ground white pepper

For the Vegetables

1 cup cherry tomatoes, halved

1 cup baby bok choy or Chinese broccoli, cut into 2-inch pieces

1/2 cup fresh straw mushrooms or cremini mushrooms, quartered

1 red bell pepper, julienned

For Garnish

1/2 cup fresh Thai basil leaves

1/2 cup fresh cilantro leaves

4 kaffir lime leaves, very finely julienned

2 Thai bird chilies, thinly sliced

2 green onions, thinly sliced on diagonal

1 lime, cut into wedges

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Equipment Needed

Large, deep skillet or braiser with lid (12-inch recommended)

Fine mesh strainer

Fish spatula or slotted spoon

Instant-read thermometer (optional)

Sharp knife

Cutting board

Serving bowls

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Instructions

Preparing the Aromatics and Fish

Step 1: Prepare the Aromatics (10 minutes) Trim the lemongrass stalks, removing the tough outer layers and using only the bottom 4 inches. Bruise each piece with the back of your knife to release the aromatic oils, then cut into 2-inch lengths. Slice the galangal into thin rounds, no need to peel. Tear the kaffir lime leaves to release their oils, removing the tough central stem if desired. Lightly smash the garlic and chilies. *Visual cue: Bruised lemongrass will have visible fibers separating and release a bright, citrusy fragrance.* Step 2: Prepare the Fish (5 minutes) Pat the fish fillets thoroughly dry with paper towels. Season both sides lightly with salt and white pepper. Set aside at room temperature while you prepare the broth. *Pro tip: Bringing fish to room temperature ensures even cooking throughout the fillet.*

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Building the Coconut Broth

Step 3: Infuse the Broth Base (8 minutes) In a large, deep skillet or braiser, combine 1 can of coconut milk with the fish stock. Add the lemongrass, galangal, torn kaffir lime leaves, shallots, garlic, chilies, and cilantro stems. Bring to a gentle simmer over medium heat, then reduce heat to low. Let the aromatics infuse for 8-10 minutes, stirring occasionally. Do not let the liquid boil vigorously. *Visual cue: Small bubbles should gently break the surface. The broth will become fragrant and slightly golden from the aromatics.* Step 4: Strain and Season (5 minutes) For a refined presentation, strain the broth through a fine mesh strainer into a bowl, pressing on the solids to extract maximum flavor. Discard the solids and return the strained broth to the skillet. (Alternatively, leave the aromatics in for a more rustic presentation.) Add the remaining can of coconut milk, fish sauce, palm sugar, and white pepper. Stir to combine and dissolve the sugar. Taste and adjust seasoning as needed. The broth should be savory with hints of sweetness and a pleasant spicy warmth. *Flavor check: The broth should taste balanced, neither too salty nor too sweet. The coconut richness should be prominent but not overwhelming.*

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Poaching the Fish

Step 5: Add Vegetables (3 minutes) Bring the seasoned broth to a gentle simmer over medium-low heat. Add the mushrooms and bell pepper to the broth. Cook for 2 minutes until slightly softened. Step 6: Poach the Fish (8-12 minutes) Gently lower the seasoned fish fillets into the simmering broth, arranging them in a single layer. The broth should come about two-thirds of the way up the fish. Cover the skillet and reduce heat to maintain a very gentle simmer. Poach for 8-12 minutes, depending on the thickness of your fillets:

3/4-inch thick fillets: 8-9 minutes

1-inch thick fillets: 10-12 minutes

1.5-inch thick fillets: 12-14 minutes

*Visual cue: The fish is done when it turns from translucent to opaque and flakes easily when tested with a fork. If using a thermometer, the internal temperature should reach 145°F (63°C).* Step 7: Add Remaining Vegetables (2 minutes) During the last 2 minutes of cooking, gently tuck the baby bok choy and cherry tomatoes around the fish. Cover and continue cooking until vegetables are just tender but still vibrant. Step 8: Finish with Lime Juice Remove from heat and add the fresh lime juice. Gently swirl the pan to incorporate. Taste the broth and adjust with additional fish sauce if needed.

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Serving

Step 9: Plate and Garnish Using a fish spatula, carefully transfer each fish fillet to a shallow serving bowl. Arrange the vegetables around the fish. Ladle the fragrant coconut broth generously over and around the fish. Garnish each bowl with fresh Thai basil leaves, cilantro, julienned kaffir lime leaves, sliced chilies, and green onions. Serve immediately with lime wedges on the side and steamed jasmine rice.

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Expert Tips for Perfect Thai Poached Fish

Choose the right fish: Select firm-fleshed white fish that holds together during poaching. Avoid delicate fish like tilapia or sole, which may fall apart.

Low and slow is key: Maintain a gentle simmer, never a boil. Aggressive bubbling will cause the fish to break apart and the coconut milk to separate.

Shake the coconut milk cans: Before opening, shake well to combine the cream and liquid. This ensures even richness throughout the broth.

Don't skip the fresh aromatics: While dried versions exist, fresh lemongrass, galangal, and kaffir lime leaves are essential for authentic flavor.

Rest before serving: Let the dish rest for 1-2 minutes after removing from heat. This allows the fish to finish cooking gently in the residual heat.

Season at the end: Adding lime juice and final fish sauce adjustments after cooking preserves their bright, fresh flavors.

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Variations

Tom Kha Style (Spicier and Tangier)

Increase the Thai chilies to 6-8 and add 3 tablespoons more lime juice. Add 1/2 cup of canned straw mushrooms and a splash of roasted chili paste (nam prik pao) for a soup-like version closer to tom kha.

Southern Thai Turmeric Version

Add 1 tablespoon fresh turmeric (or 1 teaspoon ground) and 1 tablespoon tamarind paste to the broth. Garnish with fried shallots and serve with roti or rice noodles.

Whole Fish Presentation

Use a 1.5-2 pound whole fish (scored on both sides) instead of fillets. Increase cooking time to 18-22 minutes. Present dramatically at the table.

Shrimp or Scallop Variation

Replace fish with 1.5 pounds large shrimp or sea scallops. Reduce poaching time to 3-4 minutes for shrimp or 2-3 minutes for scallops.

Vegan/Vegetarian Version

Replace fish with extra-firm tofu (pressed and sliced) and use vegetable stock and soy sauce instead of fish sauce. Add more vegetables like baby corn and snow peas.

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Storage Instructions

Immediate Storage: This dish is best enjoyed fresh, as the fish texture changes upon reheating. If storing is necessary: Refrigerator Storage: Store fish and broth separately in airtight containers. The fish will keep for 1-2 days; the broth for 3-4 days. The texture of reheated fish will be firmer but still enjoyable. Reheating: Gently warm the broth in a saucepan until simmering. Add the fish and heat through on very low heat for 2-3 minutes. Alternatively, enjoy the fish cold over rice noodles as a salad-style dish. Freezing: The coconut broth (without fish) freezes well for up to 2 months. Thaw overnight in the refrigerator. Poaching fresh fish in reheated broth produces excellent results. Do not freeze the cooked fish, as the texture suffers significantly. Make-Ahead Option: Prepare the strained, seasoned broth up to 2 days in advance and refrigerate. Poach fish fresh when ready to serve.

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Serving Suggestions

This coconut-poached fish pairs wonderfully with:

Steamed jasmine rice (essential for soaking up the broth)

Rice noodles (sen lek) for a soup-style meal

Thai-style cucumber salad

Stir-fried water spinach with garlic

Steamed sticky rice for a more substantial meal

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Frequently Asked Questions

Can I use light coconut milk? Full-fat coconut milk produces the best flavor and texture. Light coconut milk will result in a thinner, less luxurious broth. If using light, consider adding 1 tablespoon of coconut cream at the end. Where can I find kaffir lime leaves? Asian grocery stores typically stock fresh or frozen kaffir lime leaves. In a pinch, substitute the zest of 2 limes, though the flavor will differ. What if I cannot find galangal? Fresh ginger can substitute at a 2:1 ratio (use 6 inches of ginger for 3 inches of galangal). The flavor will be warmer and spicier rather than citrusy and piney. How do I know when the fish is perfectly cooked? The flesh should be opaque throughout and flake easily with gentle pressure from a fork. If the center is still translucent, continue poaching for another minute or two.

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*Recipe developed and tested in our kitchen. Last updated: 2026-01-19*

Kitchen Science: Why This Method Works

Baking relies on the Maillard reaction and caramelization to develop complex flavors. Between 280-330°F, amino acids and sugars undergo hundreds of chemical reactions that create the golden-brown crust and deep savory notes we associate with well-baked food. Understanding this science explains why proper preheating and avoiding overcrowding (which traps steam and prevents browning) are critical to achieving the best results with this recipe.

Nutrition Deep Dive

White fish varieties provide lean, highly digestible protein — typically 20-25g per 100g with minimal fat. Fish protein is absorbed more quickly than meat protein due to its lower connective tissue content. White fish is particularly rich in iodine (critical for thyroid function), phosphorus, and selenium. The low calorie density makes fish ideal for nutrient-rich, lighter meals. Even low-fat fish species contain some omega-3 fatty acids, and all fish provides vitamin D in greater quantities than most terrestrial protein sources.

Hosting and Entertaining Tips

Fish intimidates many home entertainers, but timing is the only challenge — and it's a short one. Choose thick-cut fillets (halibut, cod, mahi-mahi) that forgive a minute of overcooking better than thin, delicate species. Prepare everything else first, then cook the fish last. En papillote (fish in parchment packets) is a brilliant entertaining technique: assemble packets hours ahead, refrigerate, and pop in the oven 15 minutes before serving. Each guest gets their own beautiful packet to open at the table.

Seasonal Adaptations

Thai cuisine follows the tropical growing seasons closely. The cool season (November-February) brings the best herbs, lettuces, and lighter preparations. Hot season (March-May) calls for refreshing som tam salads, cold noodles, and spicier dishes that induce cooling sweat. Rainy season (June-October) favors warming curries, soups, and preserved ingredients. Fresh Thai basil, lemongrass, and galangal are available year-round but peak in potency during the dry months.

Food Safety Notes

Cook fish to 145°F (63°C) — the flesh should be opaque and flake easily with a fork. Fresh fish is highly perishable: buy it last at the market and refrigerate within 30 minutes. Use fresh fish within 1-2 days of purchase. When buying whole fish, look for clear eyes, bright red gills, and firm flesh that springs back when pressed. Frozen fish, when properly handled, can be equal in quality to fresh — many fish are flash-frozen on the boat within hours of catching. Thaw frozen fish overnight in the refrigerator.

Cultural Context and History

Thai cuisine balances four fundamental flavors — sour, sweet, salty, and spicy — in every meal, guided by the philosophy that harmony in food creates harmony in life. The royal court cuisine of Bangkok and the rustic cooking of the countryside represent two poles of a spectrum that encompasses incredible regional diversity. Thai cooking absorbed influences from China (wok technique), India (curries), and Portugal (chiles, originally from the Americas) and transformed them into something entirely unique.

Ingredient Substitution Guide

If you need to swap the main protein, these alternatives work well with the same seasonings and cooking method:

Cauliflower steaks: Cut thick cross-sections and season identically to the fish.

Shrimp (large): Peel and devein, cook significantly less time. Done when pink and C-shaped.

Salmon: Richer and fattier than most white fish. Reduce any added oil.

Cod or halibut: Mild, flaky white fish. Cod is thinner, so adjust cooking time.

Scaling This Recipe

This recipe serves 4, but it's easily adjusted:

When scaling up, keep in mind that spices and seasonings don't scale linearly — use about 1.5x the spices for a doubled recipe rather than 2x, then adjust to taste.

Acid ingredients (citrus, vinegar) should be scaled conservatively — start at 1.5x for a doubled recipe and add more to taste.

For halving the recipe, most timing stays the same but check for doneness 5-10 minutes earlier since smaller volumes heat through faster.

If doubling, use a larger pan rather than a deeper one to maintain the same cooking dynamics. Overcrowding changes everything.

Troubleshooting Guide

Even experienced cooks encounter issues. Here's how to recover:

If cooking unevenly, your oven may have hot spots. Rotate the pan 180 degrees halfway through and consider using an oven thermometer to verify temperature accuracy.

If the bottom is soggy, move the dish to a lower rack for the last 10-15 minutes of cooking to crisp from below.

If the top is browning too fast, tent loosely with aluminum foil and continue baking until the interior reaches the correct temperature.

Beverage Pairing Guide

Thai iced tea — that impossibly orange, creamy, sweet drink — is the classic non-alcoholic pairing, with its condensed milk sweetness cooling the chili heat. For beer, a light lager or pilsner lets the complex flavors shine without competition. Off-dry Riesling is considered the perfect wine for Thai food: its residual sugar tames the heat while its acidity matches the lime and lemongrass brightness. A Singha or Chang beer with a squeeze of lime is authentic. Coconut water provides natural, subtle sweetness that echoes the coconut milk in many Thai preparations.

Common Mistakes to Avoid

Avoid these common pitfalls for the best results:

Forgetting to rest the dish after baking — residual heat continues cooking for 5-10 minutes after removal.

Skipping the preheating step — starting in a cold oven leads to uneven cooking and longer bake times that dry out the exterior.

Using dark pans without adjusting temperature — dark metal absorbs more heat, so reduce temperature by 25°F.

Opening the oven door repeatedly — each opening drops temperature by 25-50°F and extends cooking time significantly.

Leftover Transformation Ideas

Transform your leftovers into entirely new meals:

Flake leftover fish into tacos with cabbage slaw, chipotle crema, and fresh cilantro for an easy weeknight meal.

Toss flaked fish with pasta, garlic, olive oil, capers, and lemon for a Mediterranean-inspired dinner in 15 minutes.

Mix with mashed potatoes to form fish cakes, bread lightly, and pan-fry until golden for a British-inspired treat.

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Dietary Modifications

For a gluten-free version, use rice flour or cornstarch for dredging instead of wheat flour. For dairy-free, replace butter with olive oil or coconut oil — both complement fish beautifully. For keto-friendly preparation, skip any breading and focus on herb crusts or simple pan-searing. For low-sodium, replace capers and olives (high-sodium garnishes) with fresh herbs and lemon. To make this Whole30 compliant, ensure any coating is compliant and use clarified butter (ghee) instead of regular butter.

Ingredient Selection and Quality Guide

Fresh fish should smell like the ocean, not "fishy" — a strong odor indicates deterioration. For whole fish, look for clear, bright eyes and red gills. For fillets, the flesh should be firm, moist, and bounce back when pressed. Sustainable sourcing matters: check the Monterey Bay Aquarium Seafood Watch recommendations for responsible choices. Flash-frozen fish (IQF - Individually Quick Frozen) can actually be fresher than counter fish, as it's often frozen within hours of catching on the boat itself.

Mastering the Perfect Texture

Achieving the perfect baked texture is about controlling moisture at every stage. Start by patting the surface completely dry — moisture is the enemy of browning and crispiness. A light oil coating promotes even heat transfer and Maillard reaction development. Resting after baking allows residual moisture to redistribute rather than flooding out when cut. If you want a crispy exterior with a moist interior, start at high heat (425°F) for the first 15 minutes to set the crust, then reduce to finish gently.

Kitchen Wisdom

These fundamental kitchen principles will elevate not just this recipe, but everything you cook:

A sharp knife is safer than a dull one. Dull blades require more pressure, increasing the chance of slipping. Hone your knife on a steel before every session and sharpen it with a whetstone monthly.

Learn to cook by sound. A gentle sizzle means the temperature is right for sautéing. A violent splattering means the pan is too hot. Silence in a pan that should be sizzling means the heat is too low.

Let butter brown for a nutty, complex flavor. Heat whole butter until the milk solids turn amber (watching carefully — it goes from brown to burnt in seconds) for an easy flavor upgrade.

Toast your spices before using them. A minute in a dry pan over medium heat releases volatile oils and deepens flavor — the difference between spices that whisper and spices that sing.

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Temperature and Doneness Guide

Most white fish reaches optimal texture at 135-145°F (57-63°C), where the flesh is opaque, flakes easily with a fork, and remains moist. Delicate fish (sole, flounder): Cook gently to 130-135°F to preserve their tender texture. Firm fish (halibut, swordfish, mahi-mahi): These can handle 140-145°F and still remain moist due to their denser muscle structure. Tuna: Often served rare at 115-120°F for sashimi-grade preparations. The fork test is reliable for fish: insert a fork at a 45-degree angle and twist gently — the fish should flake and separate cleanly without being dry or crumbly.

Building Your Aromatic Foundation

Thai aromatics are built from fresh pastes rather than dry spices. The classic curry paste combines lemongrass, galangal, kaffir lime leaves, shallots, garlic, and chiles — pounded in a mortar until fragrant and smooth. This paste is "cracked" in hot coconut cream (not oil) until the fat separates and the paste becomes deeply aromatic — a technique called "breaking the coconut cream." Fish sauce provides salt and umami simultaneously, while palm sugar balances the heat. Fresh Thai basil, cilantro, and lime juice added at the very end provide the bright, herbaceous finish that makes Thai food electric.

Global Flavor Riffs

Once you've mastered the base recipe, try these international variations that use the same protein with different flavor profiles:

Go West African with a tomato-based stew featuring scotch bonnet, ginger, and okra — a style of fish cookery that spans the coast from Senegal to Nigeria.

Try a British approach with a classic beer batter (lager, flour, and a touch of baking powder) for pub-style fish with malt vinegar and mushy peas.

Give this a Peruvian twist with a ceviche-style treatment: "cook" in lime juice with red onion, cilantro, and ají limo for a refreshing cold preparation.

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