Poaching is a moist heat method of cooking where food is submerged in a bath of flavorful liquid that's kept just below the boiling point (160 to 180 degrees). Seafood cooked using this technique will have a more consistent texture and milder flavor when compared with the same type that has been grilled, broiled, or baked.
Whole fillets of sturdy finfish, such as salmon, may be poached successfully, while flakier varieties may become mushy in texture or fall to pieces when the fish is fully cooked. Large shellfish, including scallops and shrimp, are excellent when poached. Smaller shellfish and bivalves tend to be less appetizing.
Cooking vessels for poaching are sold in stores-many will be large enough to hold a whole side of salmon. Most are made of two pieces; one holds the cooking liquid, the other is a removable insert that keeps the food from directly touching the bottom of the pan.
To make your own poaching vessel, find a heat-safe pot or roasting pan that's deep and wide enough to fit both the seafood and enough poaching liquid to entirely submerge it. For large pieces of fish, it's helpful to place a rack along the bottom that easily fits inside the pan. This helps to prevent breaking or flaking the fish (which becomes very fragile when cooked) as it is removed from the poaching liquid. Grasp the rack with two sets of heat-proof tongs and carefully lift the rack with the fish nicely balanced on top.
Find a basic recipe for a poaching liquid that you like and then adjust it to suit your taste preferences. Many combinations of flavorful broth, herbs, onions, shallots, spices, wine, or juices complement the natural flavors of seafood. Bring the liquid to a simmer (it's helpful to use a thermometer to make sure the liquid remains below 180 degrees, but above 160 degrees). Carefully place the seafood in the poaching liquid and cook gently until the texture firms and the meat just turns opaque. The seafood will continue to cook once it has been removed from the poaching liquid, so take it out just before it easily flakes or it will fall apart. Serve poached seafood warm or chilled.