Lobster Mac & Cheese

INGREDIENTS

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