Lobster Mac and Cheese

INGREDIENTS

• Vegetable oil
• 1/2 teaspoon nutmeg
• 1 1/2 pounds cooked lobster meat
• 8 tablespoons (1 stick) unsalted butter, divided
• 1/2 teaspoon freshly ground black pepper
• 1 pound cavatappi or elbow macaroni
• 1 1/2 cups fresh white bread crumbs (5 slices, crusts removed)
• 1/2 cup all-purpose flour
• 12 ounces Gruyere cheese, grated (4 cups)
• 8 ounces extra-sharp Cheddar, grated (2 cups)
• 1 quart milk
• Kosher salt