With cooking, it’s often true that the humblest ways of doing things are also the best. I take a lot of pleasure in this fact. For instance: Chiles ground with a mortar and pestle. Pizza cooked in a wood-fired brick oven. Fish butchered by hand with nothing but a well-sharpened knife. These are tools and methods that haven’t changed a whole lot in 5,000 years of eating. The technique of salt-roasting fits into that category: ancient, modest and pretty unbeatable.
For those unfamiliar with the method, here’s the general idea: You encase a given ingredient, such as fish, in a shell of wetted salt, place it in a hot oven to cook, then break open the salt crust and eat what’s inside. The salt works to seal in moisture and gently steam the food in its own juices, seasoning it slightly in the meantime. The finished product is invariably moist, succulent and bursting with flavor.
It’s a technique that you don’t see used a lot in this country, I think in part due to fears about dietary salt intake. But done properly, salt-roasting does not yield food that’s salty -- just perfectly seasoned. The method also has the advantage of avoiding added fat from cooking oils, which should make it a big hit with health-conscious cooks.
You can bake a lot of different things in a salt crust, but today I’m going to focus on the most traditional use for the technique: fish.
Start with a whole fish. Just about any will do, from sardines to a whole salmon, as long as you have a big enough oven. One of my favorites is sea bass (I pull them out of the Long Island Sound from June to October).
Now, the salt crust. To bring the salt together into a moldable plaster, I use two egg whites for every cup of salt. I’ve heard of people just using water, but I find that egg whites bind the salt more effectively into a crust that becomes sturdy when baked. Mix the salt and whites together with your hands. It should feel like wet sand. You’re going to need a lot of salt -- about 5 cups for a 3-pound fish.
I use Diamond Crystal Kosher salt for this task (and, for that matter, practically everything else I do in the kitchen). Some cooks say they like sel gris, a coarse sea salt, for its flavor. Sel gris works fine, but I’ve never noticed a flavor difference, and it’s about 15 times as expensive as kosher salt.
Some cooks like to add aromatics like citrus zest, herbs or spices to the salt crust. There’s no harm in doing this, but the effect on a whole fish will be very subtle. I prefer to stuff the fish’s cavity with herbs.
For a whole fish, consider using a sheet pan instead of a roasting pan. The shorter sides makes it easier to work with the fish when it comes out of the oven. Spread a bed of salt on the pan, lay the fish on top, then mold the salt mixture around it tightly, sealing up the fish entirely.
Now, place the fish in a 400-degree oven. If we’re talking about a 3-pounder, let it roast for about 25 minutes. By this point, the salt crust should have developed a warm golden patina, almost the color of sand, and be hard to the touch. Punch the needle of a meat thermometer through the crust into the fish. If the temperature measures 120 to 125 degrees, it’s ready. If not, leave it for another five minutes and check it again.
Once you’ve mastered the whole-fish technique, the process can be done with center-cut fillets too. The fact that there’s no protective layer of skin between the flesh and the salt means that the preparation is trickier. Start with a nice, thick piece of fish. I find that the technique works better on fattier fish than leaner ones. Same goes for sturdier fish. Salmon, Arctic char, sablefish: yes. Delicate ones like tilapia, flounder or sole: no.
Whether you’re using a whole fish or fillets, it takes some practice to perfect the handling of salt-roasted fish. But it’s worth the effort.
Heat the oven to 400 degrees. Clip the fins off the fish and stuff its cavity with thyme.
Using your hands, in a large bowl mix together salt and egg whites until the salt looks and feels like wet sand.
Spread a bed of the salt mixture on a sheet pan or roasting pan, lay the fish on top, and then mold the salt mixture around it tightly, sealing the fish entirely.
Place the fish in the oven and roast until a thermometer poked through the crust and into the fish registers an internal temperature of 120 to 125 degrees, about 30 minutes.
Using two spatulas, gently lift the fish out of its salt bed and onto a clean work surface (it will be tender and want to fall apart easily). Scrape off any salt clinging to the fish with the blade of your slicing knife or with a pastry brush. It’s important to be as thorough as possible with this.
Fillet the fish by slicing diagonally near the gills, and then straight down the middle of the back. Fold back the skin and lift the fillets off one at a time, followed by the skeleton, then retrieve the bottom fillets. Do a final check to make sure there are no bones or clumps of salt clinging to any of the fish portions. Serve immediately.