Baking fish in paper marries the convenience of baking with the speed of steaming. Enclosing each piece of fish in a small space with vegetables and seasonings creates a dish with its own sauce. It’s hands-off cooking and a great way to get maximum flavor with little or no added fat. I’ve used this technique, also called baking en papillote (pronounced ahn PAH-pee-YOHT), both at home and in restaurant kitchens, and I find it’s as useful for serving single portions as it is for dinner for ten.
In theory, the ingredients also could be cooked in aluminum foil instead of parchment. But I think baking in foil is slower than the almost instant transfer of oven heat through parchment. And aluminum foil cannot match the visual appeal of an oval envelope of parchment, browned and puffed from the steam within.
The proper fish for paper
The ideal thickness of fish for parchment baking is between 1/2 and 3/4 inch. Fish this size will generally cook in 6 to 8 minutes, just right for getting the paper golden brown. Dense fish like monkfish, lingcod, and wolffish should be cut thinner so that it cooks in the same amount of time.
It’s easiest to use a whole fillet; medium-size fish, such as tilapia and smaller red snapper or Pacific rockfish, yield single-serving fillets of an appropriate size. Larger fillets have to be cut into portions, and smaller fillets (from some flatfish) may have to be stacked to create the proper thickness. You can leave on the skin if you like, but be sure to scale the fish first. Freshwater fish other than farmed trout are generally better if skinned before cooking. Small fish of a half pound or less (trout, small mackerel, fresh sardines, and small flatfish, for instance) can be cooked whole, on the bone. Gut and scale them, and cut off the heads and tails if necessary to fit the package.
The only fish I generally don’t cook using this technique are “steak fish,” such as swordfish, tuna, and shark, which are more suited to dry-heat cooking methods. Lean varieties, like snapper, rockfish, and most flatfish, can use a little butter or oil to enrich the sauce, while richer varieties (such as salmon and bluefish) provide plenty of fat on their own. Shellfish like shrimp or crabmeat are excellent for accenting mild-flavored fish.
Other good things in the package
Additions to the package can range from a small quantity of aromatic flavorings to a sauce and vegetable topping—even cooked grains. Vegetables cooked in parchment must be cut in small pieces so that they’re done in the short time it takes to cook fish fillets. Dense vegetables like carrots and celery should be cut into fine julienne; quicker-cooking varieties (summer squash, mushrooms, and onions, for instance) can be cut up to 1/4 inch thick. Vegetables not suited to small slices, like asparagus, may need to be blanched.
Keep the moisture content of the vegetables in mind as well. Tomatoes release flavorful juices that become part of the sauce, but watery vegetables like summer squash can dilute the flavor of lean fish. To reduce this effect, salt watery vegetables after cutting and let them sit for at least 15 minutes to release their water before you assemble the fish packages.
In parchment’s moist baking environment, neither the fish nor the vegetables will brown noticeably. If you want a browned flavor or color, you’ll have to achieve it before the vegetables go into the paper, by roasting peppers or sautéing onion slices.