This is a version of one of Martha Stewart’s many takes on a classic. You can easily divide this recipe in half; use a 1 1/2-quart casserole dish instead.

Steps

1. Preheat oven to 375 degrees. Butter a 3-quart casserole dish; set aside.
2. Place bread in a medium bowl. In a small saucepan over medium heat, melt 2 tablespoons butter. Pour butter into bowl with bread, and toss. Set breadcrumbs aside.
3. 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.
4. While whisking, slowly pour in hot milk. Continue cooking, whisking constantly, until the mixture bubbles and becomes thick.
5. Remove pan from heat. Stir in salt, nutmeg, black pepper, cayenne pepper, 3 cups cheddar cheese, and 1½ cups Gruyère or 1 cup Pecorino Romano; set cheese sauce aside.
6. 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
7. Pour mixture into prepared dish. Sprinkle remaining 1½ cups cheddar cheese, ½ cup Gruyère or ¼ cup Pecorino Romano, and breadcrumbs over top. Bake until browned on top, about 30 minutes. Transfer dish to a wire rack to cool 5 minutes; serve hot.