Poaching has a maligned reputation. The idea that it takes a lot of time and fancy equipment is just not true. Fillets poach in about 10 minutes, and a whole fish takes only about half an hour. An ordinary, straight-sided skillet that holds seafood snugly in a single layer makes the perfect poaching vessel. For whole fish, a poacher simplifies the task, but it's not crucial.
You can improvise by placing the whole fish on a wire cooling grid in a roasting pan deep enough to allow the poaching liquid to cover the fish (for an 8-pound salmon, about 5 inches). Remove the head and tail if the fish is longer than the pan. Insert a piece of kitchen string through the wires at both short ends of the cooling grid and tie each piece to make handles for lifting out the cooked fish. Cover the pan with aluminum foil or a baking sheet.
Or consider test kitchen staffer Jennifer Cofield's method. Wrap the whole fish in a double layer of cheesecloth, twisting the ends to use as a handle. Drape the ends over the top of the fish while poaching. When done, hold the ends and pull the fish out of the pan. (Much of the skin will come off with the cheesecloth.)
The basics of poaching are simple. Start with the absolute freshest seafood you can find. There's no breading, spice mix, or smoky grilled flavor to conceal flaws--so don't use anything less than the best quality. Choose a highly seasoned poaching liquid to infuse the food with flavor. Our court-bouillon recipe for poached salmon is a basic broth perfect for any whole fish or fillets. Strain and refrigerate the bouillon up to three days (or freeze up to six months) to use for more poaching or in a stew.
Start poaching whole fish in a cold liquid, so the outside of the fish doesn't get overcooked before the interior is ready. Start with medium heat. By the time the liquid begins to simmer, the fish will be almost done. For fillets, begin poaching in simmering liquid because they will overcook if you start with a cold liquid. Bring the broth to a simmer, add the fillets, then raise the heat slightly to bring it back to a simmer. Keep the liquid for all fish simmering, not boiling. Bubbles should just barely break the surface of a broth, and this may take some adjustment of your burners to maintain. Poaching is an amazingly quick process, so be careful not to overcook the fish.
The best way to tell when a whole fish is done is by temperature: An instant-read thermometer should register 125° when inserted into the thickest part of the fish. Residual cooking will bring the temperature to a safe 140°. For fillets, or for a whole fish if you don't have a thermometer, take a peek inside the flesh with the point of a knife. When it begins to lose its opacity and flake, it's done.
Depending on the poaching liquid, you may be able to use it with the fish as a flavorful broth. Or, once the fish is removed from the pan, you can reduce it to an intensely flavored sauce. Poached fish speaks of the sea because this cooking method enhances its natural flavor. And because the fish is kept moist while cooking, poaching ensures succulent results.