Poaching fish in olive oil was astonishing to me when I first encountered it back in the 1990s. A wonderful chef named Tom Gutow had a restaurant in Castine, Maine on Penobscot Bay. Tom poached center cuts of native-raised Atlantic salmon and what arrived at the table at the Castine Inn was so fresh-tasting, so silken in texture, so utterly delicious, that it seemed quite miraculous.
Alas, the Gutows closed down the restaurant and then sold the inn so I’ve had to turn to my own kitchen for this fantastic dish.
I’ve tried the technique many times and I confess it’s a little tricky at first. But I’ve gained confidence in my ability to maintain the oil at a constant low temperature, and I turn to oil-poaching now for delicious results. Chef Tom poached his fish on top of the stove and so did I at first, but it requires constant vigilance to be sure the temperature never goes over about 150º. So now I start it on top of the stove and finish in a very low 200º oven.
A center cut of salmon, what the French call a darne de saumon, is ideal for this, but a thick halibut steak also works well. In Sicily I’ve had an oil-poached round of swordfish, cut from the tail end in one thick 3-inch piece. I imagine a center cut of yellowfin or albacore tuna, if you could find it, would be great. But failing a center cut, thick fillets of fish will also work, though they take less time to cook all the way through—which, come to think of it, might be a virtue.
Having selected the fish, set the oven on 200ºF. Use a pan that can go in the oven or a baking dish that can sit on a burner (because you’ll need to use both cooking areas) and add your fish to the pan. It’s best if the fish just fits in the pan, without too much empty space—you’ll use less oil that way. In Sicily, cooks sprinkle the fish with dried oregano, grated lemon zest, salt, and pepper. Sometimes I add a couple of garlic cloves, peeled but left whole, a couple of branches of fresh thyme, and a few small chili peppers. Now add olive oil to come just to the top of the fish and cover it with a thin film of oil.
Set the pan on a stove-top burner over minimal heat—the smallest flame on a gas burner, the lowest setting on electric. Use a frying or candy thermometer to be exact and when the oil in the pan has reached 200º, carefully transfer the pan to the oven.
(Some cooks like to craft a bain-marie, setting the pan with the fish and oil into a larger roasting pan, then adding boiling water to the roasting pan to come about 2 inches up the sides. I don’t see the necessity of this, but it seems worth noting)
Leave the fish to cook for an hour, then test for doneness. It’s hard to give precise times since it depends on the thickness of the fish, but it’s almost impossible to overcook unless you forget the fish and leave it in all day. If you’re planning a dinner party, put the fish in the oven at least two hours before you’re expecting to serve it. Keep in mind that some fish (salmon and tuna for instance) are preferred on the rare side, while others (swordfish, halibut, and the like) are better cooked through.
If the fish is not quite done, put it back in the oven, turn the heat off but leave the oven door closed, and the fish will continue to cook in the residual heat of the oil. If the fish is much more underdone than you prefer, simply continue cooking it for another 30 minutes or so.
When the fish is done, remove the pan and use a slotted spatula to transfer the fish to a warm serving platter, leaving behind the oil and the white “patina”—actually the juice of the fish that has solidified in cooking.
This photo doesn’t do justice to the appetizing look of the fish but what can I say? Blame the photographer.
Use the savory oil to make a sauce for the fish. I like a dead simple Sicilian salmoriglio, made by mixing olive oil, lemon juice, dried oregano, minced garlic, and salt and pepper.
Note to cooks: Another beauty of this preparation, because the oil is treated in such a gentle manner, it can be used two or three more times, first filtering it through a fine-mesh sieve. It will, however, be redolent of fish so use it advisedly.