You can easily divide this recipe in half: Use a one-and-a-half-quart casserole dish.
8 tablespoons (1 stick) unsalted butter, plus more for dish
6slices good white bread, crusts removed, torn into 1/4- to 1/2-inch pieces
1 tsp garlic powder
5 1/2 cups milk
1/2 cup all-purpose flour
2 teaspoons salt
1/4 teaspoon freshly grated nutmeg
1/4 teaspoon freshly ground black pepper
1/4 teaspoon cayenne pepper, or to taste
4 1/2 cups grated sharp white cheddar cheese (about 18 ounces) (wisconsin is great)
2 cups grated Gruyère cheese (about 8 ounces)
1 pound elbow macaroni (Barilla brand)
1. Heat the oven to 375 degrees. Butter a 3-quart casserole dish; set aside. Place bread in a medium bowl. In a small saucepan over medium heat, melt 2 tablespoons butter. Add garlic. Pour butter/garlic into the bowl with bread, and toss. Set bread crumbs aside.
2. In a medium saucepan set over medium heat, heat milk. Melt remaining 6 tablespoons butter in a high-sided skillet over medium heat. When butter bubbles, add flour. Cook, whisking, 1 minute.
3. While whisking, slowly pour in hot milk. Continue cooking, whisking constantly, until the mixture bubbles and becomes thick.
4. Remove pan from heat. Stir in salt, nutmeg, black pepper, cayenne pepper, 3 cups cheddar cheese, and 1 1/2 cups Gruyère or 1 cup Pecorino Romano; set cheese sauce aside.
5. Fill a large saucepan with water; bring to a boil. Add macaroni; cook 2 to 3 minutes less than manufacturer's directions, until the outside of pasta is cooked and the inside is underdone. (Different brands of macaroni cook at different rates; be sure to read the instructions.) Transfer macaroni to a colander, rinse under cold running water, and drain well. Stir macaroni into the reserved cheese sauce
6. Pour mixture into prepared dish. Sprinkle remaining 1 1/2 cups cheddar cheese, 1/2 cup Gruyère, and bread crumbs over top. Bake until browned on top, about 30 minutes. Transfer dish to a wire rack to cool 5 minutes; serve hot.