Creamy Broiled Scallops Mornay

Ingredients

• 1 teaspoon olive oil
• 6 ounces white button mushrooms
• 1 tablespoon unsalted butter
• 1 tablespoon unbleached all purpose flour
• 1 cup whole milk
• Small pinch piment d'Espelette or cayenne pepper
• Small pinch freshly grated nutmeg
• 5 tablespoons grated Gruyère, divided
• 12 ounces bay scallops
• Kosher salt and freshly ground black pepper
• 2 tablespoons chopped fresh parsley leaves
• Lemon wedges for serving

Directions

1. Set an oven rack 6 inches below the broiler, then turn the broiler to high. Warm the olive oil in a small nonstick skillet over medium-high heat until it glints. Add the mushrooms and cook, stirring frequently, until they have browned but are still a little shy of fully cooked, about 5 minutes. Move the mushrooms to a small plate.
2. Put the butter in the emptied skillet and let it melt over low heat. Whisk in the flour, then cook until the mixture turns lightly golden, about 1 minute. Pour in the milk in a slow, thin stream, whisking as you go. Keep the pan over medium heat and continue whisking until the sauce is thick enough to cling to the back of a spoon and a line drawn through it with your finger holds its place, about 5 minutes. Take the pan off the heat, whisk in the piment d'Espelette or cayenne, nutmeg, and 3 tablespoons Gruyère, and set the sauce aside.
3. Coat 2 small, wide ovensafe dishes with a light film of oil. Divide the scallops and mushrooms between them, using half of each in each dish, then season with salt and pepper. Smooth everything into an even layer. Spoon half of the Mornay sauce over each dish, then scatter about 1 tablespoon of the remaining grated Gruyère on top of each one. Broil until the tops are browned and bubbling and the scallops are cooked through, 8 to 10 minutes. Take the dishes out of the oven, let them cool slightly, add the parsley, and serve with lemon wedges.