Poaching, With Particulars, Can Handle Fish Perfectly
Wednesday, March 12, 2008
When was the last time anyone asked how you would like your fish cooked: medium, or medium-rare?
While most burger-flipping dads take pride in at least pretending that everyone is entitled to their desired level of charredness, that privilege often is denied to fish-eaters. Fish, it seems, is not something to which choice, or moderation, applies. Either it is served raw (as in sushi and its kin, the ubiquitous seared-but-still-raw-and-often-still-cold tuna) or it is seriously overcooked: the kind of dish whose success depends on a diner's goodwill, and the sauce.
When cooked gently, a slice of white fish -- cod, pollock and halibut are particularly good during the winter and up until May -- can be perfection in it simplest form. It is firm and flaky, soft and juicy, with mild, ephemeral flavors and that hint of sweetness that mysteriously finds its way into a creature that spends its life in a saline environment.
It is a paradox that home cooks don't pay more attention to the way they prepare fish even though it is so much more fragile and sensitive than meat (and in many instances much better tasting, not to mention better for you). There are no excuses for that, but many reasons. One is the way we learn to cook, with a frying pan and a pot of boiling water. Both frying and boiling are too brutal to do a fish justice.
The simplest and most appropriate way to cook fish is in water or stock: gently heating the fish to the point where proteins and connective tissue have been transformed and the fish is no longer raw. The challenge is that cooking fish has very little in common with boiling water. Water boils at 212 degrees; that is when the water molecules reach their transitional phase, that magic transformation from liquid to gas. But 212 degrees holds no magic for fish. With fish, all the interesting things happen at much lower temperatures.
Most of us consider meat from warm-blooded animals "cooked" when the core temperature has reached between 130 and 160 degrees, depending on the cut of meat and our personal preferences. For fish such as cod, pollock and halibut that live at very low temperatures -- often not much over 40 degrees -- cooking starts at much lower temperatures. Proteins begin to break down at below 100 degrees, and by 120 degrees most of the cooking processes have taken place. What happens at higher temperatures is mainly that the flesh becomes drier and tougher. That is sort of addressed by cookbooks that ask you to immerse the fish in water that simmers but does not boil. But simmering can involve anything from 160 to 210 degrees and therefore is not a useful concept, other than as a way to show that you are aware of the situation though not capable of doing much with it.
Chefs who seek perfection have a wide range of options that are unavailable or highly impractical for us mere mortals with our limited home kitchens. These days, using sous-vide and Cryovac methods, chefs can cook their fish at an ideal temperature -- say, 129 degrees -- with the use of a machine and the touch of a button. Molecular gastronomy champion Heston Blumenthal at the Fat Duck outside London has been known to serve fish cooked at 113 degrees. If the ingredient is first-class, the result is perfection every time, with a maximum amount of flavor and moisture retained. (There are some health concerns using low-temperature cooking techniques. More on that later.)
Most of us are not going to spend thousands of dollars on high-tech equipment for our homes. Cooking will, I think, for the foreseeable future still be conducted in pots and pans in kitchens that are kitchens, not laboratories.
Is there no way to achieve perfect results at home without the expensive equipment?
Some of my best meals ever have been at New York's legendary four-star fish restaurant, Le Bernardin. Chef Eric Ripert does not reject the findings of modern food science, but he has little interest in finding a gadget-based solution for what should be the challenge of the cook.
"With fish, you have to be so focused," Ripert says. "You can't turn away and do something else. If you forget about the fish in the pan, then you are not doing the job. But I don't think that technology is the answer. Cooking fish using vacuum, or wrapping it in plastic, it just doesn't work for me."
I have experimented with low-tech home-based sous-vide methods for some time. One of them involves wrapping the fish in plastic, adding it to water that holds the desired temperature and waiting until the fish holds the same temperature, which for a 1 1/2 -inch-thick slice of fish might take about an hour. (Because the temperature is low, you cannot overheat or overcook the fish.) To ensure that the temperature in the pot does not fall, one must always be at hand, constantly watching the thermometer and adding a splash of hot water every time the temperature starts to drop.
But although the result is very good, I am pretty certain that this must be the most annoying way to cook -- ever. Yes, I want to eat fish that is perfectly cooked. But at the same time I do not want to be bored to death. If the price of perfection is standing next to a pot for an hour with a thermometer and some hot water, then the price is too high.
Salmon is one of those fish that are constantly mistreated by cooks who think of them as meat that swims. The result makes it seem somehow inferior. But once you master how to cook salmon gently, you'll understand why it was long considered the king of fish.
At Le Bernardin, Ripert uses a technique for cooking salmon that renders the fish "soft and juicy, with texture almost like custard." It is similar to a classic French frying technique -- a l'unilateral -- in which fish is fried skin side down until it is heated all the way through. But Ripert's method is gentler. He covers the bottom of the pan with a quarter-inch or so of water and cooks the fish from the bottom. That demands a bit of knowledge and a lot of dedication and concentration, and it is easiest to get a consistent result if you trim the fish to the same thickness all over.
Another path to perfection, or near-perfection, is available to even the most restless home cook: a measured poaching technique. It is basically a convergence of weight, volume and fourth-grade math and is similar to old-fashioned poaching. Water (or stock) is brought to a boil, fish is added, and then the pot is taken off the heat. The fish will cook in gradually cooler water. The secret is to adjust the amount of water to the amount of fish, thus preventing overcooking the fish. After some trial and error I have found that using a ratio of about three parts water to one part fish (by weight) will ensure a fish that is -- using a terminology normally reserved for meat -- medium-rare, which is my ideal. (The core temperature is about 120 degrees.) My wife likes it medium, which calls for a ratio of about four to one.
The perfectionist may object that it is not ideal to use boiling water at all: Some parts of the fish, namely the surface, will invariably be overcooked. I say the disadvantages -- a few millimeters of overcooked surface -- are outweighed by the advantages. The most obvious is that we can all determine when the water is in fact boiling, so no thermometer or other equipment is necessary. The other advantage is the health aspect: Unless the fish is sushi quality, safe to consume at any temperature, it will be the host of bacteria and microbes -- mostly on the surface. Using boiling water as part of a low-temperature cooking process is a way to solve one of the inherent problems with low-temperature cooking, as the heat of the water will kill any bacteria on the surface of the fish.
At the same time, the addition of cold fish will quickly lower the temperature of the water, so the fish will continue cooking at a nearly ideal temperature. And by the time I have set the table and poured the wine, the fish is done.
Andreas Viestad is the author of "Kitchen of Light" and "Where Flavor Was Born," the host of the public television series "New Scandinavian Cooking" and co-host of the forthcoming series "Perfect Day." He can be reached at firstname.lastname@example.org or email@example.com. His Gastronomer column appears monthly.