Why This Recipe Works: When it comes to methods for cooking fish, braising is often overlooked. But this approach, which requires cooking the fish in a small amount of liquid so that it gently simmers and steams, has a lot going for it: As a moist-heat cooking method, braising is gentle and thus forgiving, all but guaranteeing moist, succulent fish. Plus, it makes a one-pot meal since the cooking liquid becomes a sauce, and it’s easy to add vegetables to the pan to cook at the same time. We chose halibut for its sweet delicate flavor and firm texture that made for easier handling. Because the portion of the fillets submerged in liquid cooks more quickly than the upper half that cooks through in the steam, we cook the fillets for a few minutes in the pan on just one side and then braise the fillets parcooked side up to even out the cooking. Vegetables that held their shape but cooked through quickly worked best. For the cooking liquid, wine supplemented by the juices released by the fish and vegetables during cooking delivered a sauce with balanced flavor and just the right amount of brightness. Butter gave it some much-needed richness and the right velvety texture.

• 4 (6- to 8-ounce) skinless halibut fillets, 3/4 to 1 inch thick
  • Any firm white fish will do. Make sure all fillets are the same thickness.
• Salt and pepper
• 6 tablespoons unsalted butter
• 1 pound leeks, white and light green parts only, halved lengthwise, sliced thin, and washed thoroughly
• 1 teaspoon Dijon mustard
• 3/4 cup dry white wine
• 1 teaspoon lemon juice, plus lemon wedges for serving
• 1 tablespoon minced fresh parsley

1. Sprinkle fish with 1/2 teaspoon salt. Melt butter in 12-inch skillet over low heat. Place fish in skillet, skinned side up, increase heat to medium, and cook, shaking pan occasionally, until butter begins to brown (fish should not brown), 3 to 4 minutes. Using spatula, carefully transfer fish to large plate, raw side down.
2. Add leeks, mustard, and 1/2 teaspoon salt to skillet and cook, stirring frequently, until leeks begin to soften, 2 to 4 minutes. Add wine and bring to gentle simmer. Place fish, raw side down, on top of leeks. Cover skillet and cook, adjusting heat to maintain gentle simmer, until fish registers 135 to 140 degrees, 10 to 14 minutes. Remove skillet from heat and, using 2 spatulas, transfer fish and leeks to serving platter or individual plates. Tent loosely with aluminum foil.
3. Return skillet to high heat and simmer briskly until sauce is thickened, 2 to 3 minutes. Remove pan from heat, stir in lemon juice, and season with salt and pepper to taste. Spoon sauce over fish and sprinkle with parsley. Serve immediately with lemon wedges.