Halibut with mushrooms

1 / 4 cup olive oil

4 tablespoons unsalted butter

4 large leeks, white and light-green parts only, cut into thin matchsticks, well washed, and dried (about 10 cups)

4 shallots, thinly sliced into rings (1 cup)

8 medium garlic cloves, thinly sliced

Coarse salt and freshly ground pepper

10 halibut fillets (each 6 ounces, 1 inch thick; preferably square cuts), skinned

2 pounds oyster mushrooms, halved if large

Chive Oil,
for drizzling

Beet Salad,
for serving

Preheat the oven to 400F. Heat 2 tablespoons oil and the butter in a large skillet over medium heat. Add the leeks, shallots, garlic, and Δ teaspoon each salt and pepper. Cook, stirring, until the leeks and shallots are translucent, about 3 minutes. Spread into 2 9 x13-inch baking dishes, dividing evenly. Top with the fish; season with salt and pepper. Set aside.
Heat 1 tablespoon oil in the same skillet over medium heat. Add half of the mushrooms and ÿ teaspoon salt. Raise heat to medium-high; cook, stirring, until tender, 3 to 5 minutes. Scatter the mushrooms over the fish. Repeat with the remaining oil and mushrooms and 1/2 teaspoon salt.
Bake until the fish is cooked through, 18 to 20 minutes. Transfer to plates. Drizzle with chive oil. Serve with beet salad.

SERVES 10