When I was poaching a piece of salmon a couple of years ago, I accidentally turned off the burner before the cooking was done. That salmon was one of the best I’d ever cooked. The flesh was silky; the flavor was mild and not at all fishy. The only problem was figuring out what I had done.
After playing with the idea for a little while, I came up with what I thought was a brand new method for cooking fish. It couldn’t be simpler:
You place the piece of fish in barely simmering liquid, allow it to remain over the heat for one minute, then remove it from the heat and cover it, leaving the fish to steep in the liquid until it is fully cooked, about six minutes per half-inch thickness of flesh.
What makes it work is the way the temperatures of the food and the liquid interact. When the fish is added to the simmering liquid, the liquid cools as the raw fish absorbs the heat. The idea is for the fish to be done by the time the two temperatures are the same.
The cooking time depends on how quickly the fish will heat through--which is affected by the thickness of the fish and the density of its texture--and on the ratio of liquid to fish.
It sounds complicated, but it’s really quite simple. A single scallop placed in a quart of hot fish stock is hardly going to cool the liquid by absorbing its heat. It will cook immediately. On the other hand, an inch-thick piece of dense-fleshed swordfish barely covered with liquid will probably never cook much beyond rare, no matter how long you leave it.
Use a heavy skillet or pot made from a material that will retain heat, such as enameled cast iron, steel, stainless steel or lined copper. The skillet should be deep enough for you to cover your fish by 3/4 inch of liquid. (The exception to this is when you want the fish to be rare or barely cooked, as in the tuna recipe that follows.)
What I like about this way of cooking fish is its gentleness. The liquid is not quite hot enough to make the flesh “seize” and toughen. Since only a little heat is applied to the fish after it enters the broth, there’s no risk of overcooking. Because the protein in the flesh has not fully coagulated, the resulting texture is smooth and silky. Fish emerges from the broth less damaged than after poaching or steaming.
Oily fish--salmon, trout, mackerel and bluefish, in particular--benefit greatly from this method, because the cooking temperature is never high enough to excite the volatile oils that cause “fishiness.” On top of all this, there is an exchange of flavor between the cooking liquid and fish that enhances the flavor of both. The cooking liquid makes a natural base for a quick, simple sauce.
This is a great way to cook whole fish for a cold buffet, but even something as simple as a shrimp cocktail will be improved. The shrimp will be firmer when you stop boiling them and let them cook slowly.
But as for that thrill of discovery, it was short-lived. Not long after, I was thumbing through Madeleine Kamman’s “The New Making of a Cook” (William Morrow, $40) and came across the same way of preparing fish. She refers to it, curiously, as crimping, and says she was introduced to it by an English friend.
Though the word doesn’t show up in any dictionary in relation to cooking fish, Kamman says the technique is also described by Escoffier, although apparently he did not practice it much (I wonder whether Escoffier also turned off the wrong burner one day).
Even more recently, a fellow shopper in a Parisian open-air market said he used this same method for cooking fish at home. The fish cooks while the family is enjoying the first course.
I smiled to myself and was reminded that with cooking, as with most other endeavors, when you think of something new, you can be sure that someone else has already thought of it.