4 swordfish steaks or other suitable cuts, each 1-inch thick
Kosher salt and freshly ground black pepper
4-6 cups good quality but modestly priced olive oil (see note)
Straight-sided pan large enough to hold all fish in 1 layer
Bring fish up to room temperature if removing from refrigerator, at least 1 hour ahead. Heat oven to 225F. Season fish on both sides with salt and pepper. Pour oil into pan and heat over stovetop burner until oil is 120-130F (use instant-read thermometer). Slip pieces of fish into pan and immediately place in oven. Let poach for 25 minutes. To serve: remove fish with slotted spatula or spoon.
Note: It's not necessary, of course, to use your expensive drizzling oil for this recipe. Also, you may filter the oil, once used, for another fish poaching; it will remain OK in the frig for a couple of weeks, in the freezer for a couple months.
Tips on buying, storing and cooking fish:
— When buying fresh, stretch out your thumb and first finger. Fresh fish must feel like the pad of flesh in between them, never mushy like the same pad when relaxed.
— If the fish seller allows you to sniff, it should smell neutral, at most like a sea breeze and, of course, never “fishy.” If the seller won't let your nose near the fish, see if she will fan its aroma toward your schnoz.
— A whole fish makes for cool cooking, so don't shy away from buying such. Taut skin and scales; bright red, moist gills; shiny clear eyes - all are good signs.
— It’s risky to refrigerate fish for more than a day after you buy it. After the trip to the store, keep it in a closed plastic bag set atop a bowl of smashed ice. Use the back of the lowest shelf above the bottom bins, the coldest place in the icebox.
— Keep on the skin of more delicate types of fresh fish (sole, flounder, halibut) and also salmon. The skin not only helps hold the fish together when eventually cooking it, but also adds flavor. (Score skin lightly with a very sharp knife or razor blade when cooking to prevent curling under the heat.)
— With certain sorts of fish (for example, salmon), when preparing to cook, run your fingertip over the filet to feel for "pin" bones, little pesky pains that run perpendicular to the backbone or rib cage and that lie hidden in the flesh. Remove them with tweezers, pulling "along and away" more than up and out.
— Patting fish dry before cooking ensures crispness of both skin and flesh.
— When cooking fish, many cooks adhere to the "10 minutes per inch" injunction; that is, whatever the method, they cook fish for 10 minutes for every inch of thickness of the flesh.
— But that adherence rules out considerations such as the firmness or fat content of the fish (or, looked at another way, the delicacy or leanness), or whether, in some methods of cooking over direct heat, the left-on skin provides, in effect, a heat shield.
— It's better to tailor the cooking method - sautéing or frying in a pan; deep-fat frying; roasting or baking; poaching; or grilling - to the type of fish.
— For example, the more tender chicks of the sea such as flounder, sole or halibut are well suited to sautéing, ill-suited for grilling (unless they are the whole kahuna, nose to tail and both sides now). Grilling is great for “the cows that swim” that are tuna, swordfish, mahi-mahi or, often, salmon. Their firm, sometimes-fatty flesh is like fish beefsteak.
— Packets of fish, in crimped parchment paper (“en papillote”) in the oven, are ideal for fish such as cod, pollock, sole, haddock, snapper, halibut, trout, char — in short, many a white fish and any that are delicately fleshed.
— Slowly poaching in the oven - submerged in a court bouillon, or white wine, or good quality olive oil - filets of firm-fleshed fish such as salmon, tuna or swordfish, turns out such diaphanously delicate fish flesh that it's like pudding with gills.
— If you bake or broil fish, be sure the flesh is dense, firm and well-fatted. The latter character will baste the fish as it cooks.