1Heat oven to 375 degrees. Butter a 3-quart casserole dish and set aside.
2Place bread in a medium bowl. In a small saucepan over medium heat, melt 2 tablespoons butter, pour into the bowl with bread, and toss. Set breadcrumbs aside.
3Pull out 1 1/2 cups of grated cheddar and 1/2 cup Gruyere, and reserve.
4Fill a large pot with water, bring to a boil, and add salt. Add macaroni and cook 2 to 3 minutes less than manufacturer’s directions. Transfer to a colander, rinse under cold water, and drain well.
5In a medium saucepan over medium heat, heat milk. In the pot used for the pasta, melt remaining 6 tablespoons butter. When bubbling, add flour and whisk for 1 minute.
6Slowly pour in hot milk while whisking constantly. Continue cooking and whisking until mixture bubbles and thickens. Remove from heat.
7Stir in salt, nutmeg, black pepper, cayenne pepper, 3 cups cheddar cheese, and 1 1/2 cups Gruyere. Add cooked macaroni to the sauce and stir.
8Pour into prepared dish. Sprinkle with reserved cheese and breadcrumbs. Bake until browned on top.
Ingredients
8 tablespoons unsalted butter
more for dish unsalted butter (optional)
6 slices white bread, crusts removed, torn or diced into 1/4- to 1/2-inch pieces