While fish has a reputation for being finicky—falling apart or drying out all too easily—with a little loving care, you can cook it to flaky, tender perfection. If you want a totally fool-proof method, cooking en papillote (in parchment or foil packets) is a great choice. But you could go one better and poach your fish in oil, for the most succulent piece of tuna, salmon, halibut, or cod you’ve ever had.
It’s basically confit for fish instead of duck, and it’s almost impossible to overcook it using this method, plus you can change up the flavorings any way you like. Despite what you might think, the fish doesn’t come out sodden with grease, just lightly slicked—even more lightly if you blot the surface gently with a towel before serving—and rich and silky straight on through. True, you miss out on crisp-seared skin, but you can always add a crunchy element to the plate for contrast. (That crunchy element could even be the skin itself, if you trim it off first and turn into pescatarian bacon of sorts…)
Here’s what to do:
1. Select your fish. Oil poaching works particularly well for firm, meaty fish like tuna, salmon, swordfish, halibut, and mahi mahi. However, you can try it with any other type, from tilapia to flounder, and even shrimp or scallops. For fish fillets, you can leave the skin on (it’ll slip right off later), but for shrimp, peel and devein them before poaching. You can let the fish sit out at room temperature for 15 to 30 minutes beforehand for faster cooking, but it’s not necessary either.
2. Select your oil. You don’t want to use the most expensive, super-premium olive oil you can find for this, but you also don’t want it to be bottom-shelf stuff. Choose an oil that tastes good on its own that’s also in a price range you’re comfortable with, or go for a more neutral type, like canola, avocado, or grapeseed oil.
3. Select your aromatics and seasonings. Garlic, lemon, and fresh or dried herbs like thyme and dill are classic flavors, but you can choose other combinations if you like—think ginger and sesame, fennel and saffron, or red pepper flakes and orange zest, all of which will infuse the oil and flavor the fish. Or, you can keep it simpler with just salt and pepper, and then dress the fish with a more complex sauce when it’s done.
4. Place the fish and aromatics in a baking dish. Spread your fish in a single layer in a relatively deep vessel that will hold them snugly; what kind you use depends on how much fish you’re cooking, and what form it’s in (for instance, an 8-inch square pan might suffice for cooking two tuna steaks, but you’ll need a casserole dish for a whole side of salmon). In addition to being large enough to hold all your fish, it should be at least one or two inches deeper than your fish is thick, because you’ll need to cover it completely with the oil. Try to use a dish that’s not too wide for the same reason, so you don’t have to use extra oil to fill that empty space (or fill it up with other, cheaper ingredients, like halved lemons, before adding the oil to reduce the total volume you’ll need). Tuck your flavorings like citrus slices and herb sprigs evenly in among the fillets or steaks and sprinkle a little salt and freshly cracked black pepper over all of that (plus any dry spices you may be using), then rub gently into the surface of the fish for good measure.
5. Pour over enough oil to cover it. You just want to submerge it so no part of the fish is peeking above the surface, but you don’t need to cover it by too much (about 1/8 to 1/4 of an inch should do). However, depending on the size of your pan and pieces of fish, this could take two or more cups total, which is why you probably don’t want to use a $40 bottle of olive oil here…
6. Place it in a 275 degree oven until it’s done. Depending on the thickness of your fish, this could take anywhere from 15 minutes to about an hour (or more); just check it now and again, and if any spots are no longer covered by oil when you do peek, baste them with a few spoonfuls from the surrounding pool (if you pour more oil in, it will lower the temperature and increase the cooking time). You’re looking for the flesh to be mostly opaque and fairly firm to know it’s done, but for fish like tuna and salmon in particular, if you prefer a rosier center, you can pull it out before it’s totally cooked through. However, if you do want it all the way done, it should still come out perfectly moist thanks to the oil bath.
Then what do you do with it?
Aside from serving the oil-poached fish right on a plate with some rice or grains, cooked vegetables, and perhaps a sauce (like chermoula, chimichurri, romesco, cilantro-lime sauce, or herbed yogurt sauce) or chunkier relish (like tomatillo salsa or tomato jam), you can use it to make the best tuna salad of your life; break it up and gently mix it into pasta; turn it into salmon or tuna rillettes for a fancy appetizer or snack; or serve it as part of a composed salad (like Tuna Niçoise).
Variations: You can adapt the method to the stovetop for smaller pieces of fish or shrimp and scallops. Many recipes will have you heat the oil to a specific temperature before adding the seafood, but it’ll work fine if you just combine everything in a deep pot or Dutch oven and place it over low heat until it warms up. Ideally, the oil will feel warm to the touch without being hot enough to burn you, but if you’d rather not stick your finger into cooking oil, just keep an eye on it and never let it get above a very gentle simmer, if even that. Depending on your fish (and your stove), it can take anywhere from 5 to 30 or more minutes; trust your eyes and sense of touch to know when it’s done. Whether you’re cooking in the oven or on the stove, instead of using oil, you can also poach fish in butter.
Notes: Don’t discard the oil! Or at least not all of it. You can drizzle a bit over the fish and any vegetables you’re serving with it as an ultra simple pan sauce, or use it for dipping crusty bread on the side; even incorporate it into a dressing if you’re serving the fish on or accompanied by a green salad.
If you’re still startled by the notion of cooking seafood submerged in fat, you can try this passive poaching method using water, wine, or broth instead. But for those times you’re after a truly luxurious bite, try the oil poaching method and say goodbye to all thoughts of dry, disappointing fish.
Header image courtesy of Coley Cooks.