I started my work on this article by asking a simple question: Is it better to poach or steam salmon when you want to gently cook it? I had my test set up: two pots, one full of a court bouillon—an acidic and aromatic poaching liquid traditionally used for seafood—and the other with water and a steamer insert. I was just about to bring both pots to a simmer before adding the fish, when I realized I'd asked the wrong question. Instead of comparing traditional poaching to steaming, I should have been comparing cold-start poaching to steaming.
See, we've been having a lot of success here at Serious Eats in recent months with the cold-start poaching method, in which the food is added to the pot while the water is cold, then gently brought up to temperature and cooked just to the desired doneness. It works wonders for shrimp, whether in salads or in a classic shrimp cocktail, and it makes a much tenderer and juicier poached chicken breast.
Cold-start poaching is a method that makes a lot of sense. To understand why, it helps to think about the main reasons for using high heat. Usually, we use high heat with dry cooking methods, like roasting and grilling, when we want to brown and crisp the surfaces of our meats. High heat helps a ton in those situations, because it quickly drives off moisture, paving the way for the dehydration and browning reactions that produce the flavorful crust we're after—plus, it does it fast enough that the food remains perfectly cooked and juicy within.
But when we poach, we don't want our meat and fish to brown, so high heat, even as high as boiling water, is unnecessary. And not only is it unnecessary, it's counterproductive, causing the meat's proteins, especially those near the surface, to tighten and become tough. If my chicken is perfectly done at an internal temperature of 150°F, and my salmon is ready at 115°F, exposing them to simmering- or boiling-water temperatures is well beyond what's required. This is, in essence, the primary idea behind sous vide cooking, in which food is cooked to precise temperatures in a carefully controlled water bath.
With that in mind, I changed tack, lowering my salmon fillets into the cold court bouillon and then heating it up from there; I tried to keep the poaching liquid temperature below about 170°F the whole time, just by regulating the heat. Meanwhile, in the other pot, I steamed the salmon as planned. I removed all the fish when it registered 115°F at the center and let it rest for five minutes.
The results speak for themselves. In the photo below, the two samples of salmon on the left are from the cold-start method, while the two on the right are steamed. Even though they were all cooked to the same temperature at the center, the steamed salmon ended up overcooked, presumably due to more drastic carryover cooking—since the steamed fish was cooked with higher heat, the extra heat retained in the outer layers then penetrated into the center, even after the fish had come out of the pot.
Interestingly, there wasn't a huge time difference between the steaming and the cold-start poaching methods. By the time I'd taken the steamed fish out of the pot, the cold-start poached fish was also ready.
The answer to my question, therefore, isn't to steam or poach in the traditional sense, but instead to drop the fish in cold poaching liquid and gently cook it from there. In fact, I found that you don't even need to pre-make the court bouillon—simply adding lemon juice and a few aromatics to the cold water is enough to gently flavor the salmon. (I usually discard the poaching liquid, which I suppose could be considered a downside, but thus far I haven't found a great way to reuse court bouillon.)
After that, you can eat the salmon right away while it's still warm, let it return to room temperature, or even serve it chilled from the fridge. A simple sauce, like the yogurt and dill one pictured here and included in my recipe, makes for a very quick, easy, and delicious meal.
So don't wait: Get poaching! Just, you know, chill.