Fish is poached by completely submerging it into barely simmering broth. Braising is a similar process with much less liquid. As the fish cooks its juices are absorbed into the broth, adding flavor and texture.
In a similar way the juices of the broth are also absorbed into the fish in a like exchange.
Poaching means cooking the fish without boiling, so as to coagulate the proteins and gel the collagen. If the cooking is prolonged or too much heat is used the fi bres start shrinking, and the collagen still liquid
between the fibres escapes into the broth. What could have been a succulent piece of fish turns into a dried out disaster. The surface of the liquid will begin to shudder when ready to cook the fish, and the flame should be regulated at that level until finished. Never let the liquid boil during poaching.
Assertive fish like Salmon, delicate Rockfish and Sea Bass all benefit by being poached with aromatics - thyme, fronds of fennel, corriander stems and roots, bay leaves, ginger, garlic, onion, celery, dill, chopped carrots - a glass of white wine, some vinegar, lemon juice and lemon zest, a good spoon of olive oil and enough water to float the fish. The fish is placed into the liquid, cold for whole fish - simmering for filets or steaks, and cooked at a low simmer (a shuddering liquid) until almost cooked through, then left to cool in its own liquid.
Poached fish provide a subtle, clean taste and texture for pairing with bold straightforward sauces. One of the classics is poached Salmon, which is a timeless classic for good reason. Once you have
poached Salmon successfully experiment as widely as you dare with different aromatics, herbs, and spices and of course varieties of fish.