How to Poach Fish

Poaching fish involves cooking it gently in a simmering liquid. This method of cooking is particularly appropriate for firm fillets, such as salmon fillets, and small whole fish.

The Poaching Liquid

Fish can be poached in salted water or court bouillon, which is a name given to liquids used in cooking that contain a mix of ingredients. When making a poaching liquid, follow these guidelines:

Add an acidic ingredient: The liquid should contain an acidic ingredient (vinegar, dry wine, beer, or lemon juice), which produces a chemical reaction that moderates the strong odor that is released as fish cooks. It also improves the flavor and congeals the flesh, keeping it firm.
Other ingredients you can add: In addition to the acidic element that should be added to the poaching liquid, other ingredients commonly added to the court bouillon are garlic, salt, pepper, celery, onions, carrots, thyme, fennel, bay leaf, and curry. Court bouillon made with milk is particularly appropriate for smoked fish, turbot, and skate.
Simmer: To enhance the flavor of the court bouillon, let it simmer for about 20 minutes before adding the fish.
Don’t add salt: When poaching salted fish, do not add any additional salt to the cooking liquid. If the fish has to be poached for a relatively long time, reduce the amount of salt to prevent it from becoming too salty.
Uses for the liquid after poaching: After poaching fish, you can use the leftover liquid, which is rich in nutrients as well as flavor, as stock to make a sauce.

How to Poach Fish

Place the fish in a pot with just enough cold poaching liquid to cover the fish. It’s easier to remove the fish from the pan if it’s first placed on a grill or in a piece of muslin.
Slowly bring the liquid to a simmer. The fish will cook evenly if the temperature is increased gradually.
Don’t allow the liquid to boil, because the flesh of the fish will crumble and lose more of its flavor. The outside of the fish will also cook faster than the inside.
Cook the fish for the amount of time called for in the recipe. If the fish is to be served cold, cook the fish for a few minutes less.
Allow the fish to cool in the cooking liquid.

How to Cook Fish au Bleu

Cooking fish au bleu involves poaching small fish (carp, trout, perch, pike) in liquid containing vinegar, salt, and other seasonings when the fish have been dead for less than 2 hours. It is important that the fish still be covered with their natural sticky coating—they should be gutted but not scaled. The fish become blue when cooked as the result of a chemical reaction involving the sticky coating and the vinegar in the court bouillon.

Sprinkle both sides of the fish with approximately 1/3 cup of vinegar, then cook them in a very vinegary court bouillon.
The fish can also be sprinkled with vinegar in the dish in which they’re cooked. The vinegar then becomes part of the vinegary court bouillon, which becomes that much more acidic.
Cook the fish for 8–10 minutes.

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