Martha's Macaroni and Cheese Recipe - (5/5)

Ingredients

• 6 slices good-quality white bread, crusts removed, torn into 1/4- to 1/2-inch pieces
• 8 tablespoons (1 stick) unsalted butter, plus more for dish
• 5 1/2 cups milk
• 1/2 cup all-purpose flour
• 2 teaspoons kosher salt
• 1/4 teaspoon freshly grated nutmeg
• 1/4 teaspoon freshly ground black pepper
• 1/4 teaspoon cayenne pepper
• 4 1/2 cups (about 18 ounces) grated sharp white cheddar
• 2 cups (about 8 ounces) grated Gruyere or 1 1/4 cups (about 5 ounces) grated pecorino Romano
• 1 pound elbow macaroni