Barton Seaver wants me to touch his sablefish. The brined 5-ounce fillet, cooked for 12 minutes at 154 degrees in a boxy little oven at Hook, lies unadorned on a plate. No sauce, no accompaniments. The chef pokes the fish with his finger, and I do the same. It feels firm and meaty, not dry and flaky or even moist and flaky; its consistency reminds me more of a day-boat scallop than a fillet.

“You feel that?…It feels almost the same [as when it went into the oven],” Seaver says. He slices off a small section of the fillet with the back, not the side, of a fork. The fish offers barely any resistance. Every square millimeter of the freshly exposed flesh looks moist, and Seaver can’t resist a little bleacher-bum braggadocio, as if he’s sizing up a Nats prospect.

“See the sheen on it? That’s the inside!” Seaver gushes. “The inside has that much moisture in it still. Fuck yeah, baby!”

When I finally put a forkful of the fish in my mouth, I lose all decorum myself. “That’s fucking delicious,” I exclaim. “You know what the weird thing is? It tastes like butter.”

“Well,” Seaver notes, “that’s sable.”

At the moment, Seaver couldn’t be prouder because, without knowing it, I’ve just aced his test. One of the principles on which Seaver has built his Georgetown restaurant—aside from serving sustainable seafood—is simple preparations. He wants his fish to taste like, well, the fish he so carefully buys. He doesn’t want them to serve as protein carriers for cream sauces or compound butters or some overly perfumed risotto with peas and pancetta.

That may sound like an honorable, if not overly original, organizing principle, but then you start looking at the methods for cooking fish. Grilling, baking, broiling, steaming, frying, poaching—they all, in some way, alter the natural flavor and texture of fish. Some add fat or smokiness, some create a crusty exterior, some reduce a fish’s natural moisture content. I mean, short of biting into a slice of unadorned sashimi, who the hell knows what most fish actually taste like?

The truth is, I just learned that sablefish tastes like butter when I sampled the fillet at Hook. And the only reason I could make that connection is because Seaver has apparently devised a new way to cook fish. He has adapted his oven known as the Cvap—short for “controlled vapor”—to turn out moist, pristine pieces of fish that may be the next best thing to sashimi.

When he invested in the new Cvap technology, Seaver wasn’t even sure the oven would do what he wanted. The machine, with its dual heat sources, can roast and even imitate sous vide (that controversial technique of slow-cooking vacuum-packed food in a water bath), but hotels often rely on it merely to cook and hold dishes. Seaver, however, wasn’t remotely interested in the convection-oven option for the Cvap. In fact, he hasn’t turned it on since Hook opened in April.

What fascinated the chef was the technology that gives the Cvap its name. A separate control heats a water pan at the bottom of the oven, creating what Seaver calls a “100 percent moisture environment” inside the machine. A cook can set the temperature of Cvap’s water evaporator, either to hold food at a desired doneness or to cook a piece of meat or fish at a low temperature—sous vide without the plastic bag, in other words.

No matter how chefs use the water pan, though, the key to the device is the air moisture in the oven. Seaver offers an example: “If the air has 90 percent moisture, it can only suck out 10 percent more [from the meat or fish],” he says. But because the Cvap’s humidity is complete, “it’s not sucking out the protein, therefore the liquid in the protein has nowhere to go, so it stays there. It’s pretty ingenious.”

Seaver’s science lesson boils down to a simple calculation really. More natural moisture equals more natural flavor. Retaining a fish’s moisture content has another benefit, too: A cooked fillet will better maintain its original texture, as Seaver proved with the sablefish.

Hook, unfortunately, can’t send all its fish through the Cvap unit. The machine works best, Seaver says, on more delicate fillets such as halibut and sablefish. The moist, slow-cooking process tends to make a mess of bass, snapper, or any fish with a lot of connective tissue. “When slowly roasting a piece of bass, it doesn’t taste great. The texture is bad,” Seaver says. “You need to sort of break down those bonds, and you do that through intense heat.”

The painful part, to Seaver at least, about developing a technique that emphasizes fish’s true flavor is that not everyone enjoys a taste of the sea. “Some people are saying, ‘The halibut’s really bland here,’” Seaver acknowledges. “Well, yeah, that’s halibut.…I think when I go to a place and I get a piece of halibut that’s been seared until it’s a crispy, golden, dark brown…it doesn’t taste like halibut.”

Seaver’s naturalistic approach to fish runs counter to the more-is-more philosophy of many seafood houses, just as his shtick as chef defies the industry standard of a fleshy toque in pristine whites worrying obsessively over his latest gastronomic creation. The lean Seaver prefers to project the image of an iconoclast. When I met him, he was wearing a baseball cap, T-shirt, and shorts in the kitchen, the latter of which exposed the D.C. flag tattoo on his right calf.

What’s more, his thoughts rarely seemed to stray far from his main concern: depletion of the world’s marine resources, which, believe it or not, dovetails with his approach to cooking. If we’re going to eat salmon, tuna, and the rest of these precious fish, Seaver wants us to savor every bite of them in their most natural form. It’s a philosophy that seems to polarize those eaters who want to de-fish their fish.

I called Rob Klink, executive chef at downtown’s Oceanaire Seafood Room, to get his take on Seaver’s newfound use for the Cvap. At first, the chef thought that his Rational Combi-Oven, with its light pressurized steam, performed essentially the same function as Cvap’s water evaporator. But the more I told him about Seaver’s 100-percent moisture approach—and the kind of buttery sablefish it produces—the more Klink realized his machine didn’t measure up.

The Cvap “sounds good, I’m not going to lie to you,” Klink confesses. “How much did that thing cost?”

I tell him the price Seaver quoted to me—$3,000, which stuns Klink. “Really?” he says. “It’s cheaper than ours. The Combi’s like 30.” Thirty, as in $30,000.

“It sounds like more of us should be doing it.”

Hook, 3241 M St. NW, (202) 625-4488.