Cook macaroni following package directions; drain and rinse in a colander under hot running water.
Combine the bread crumbs with 2 tablespoons of melted butter; set aside.
Preheat the oven to 375°. Grease a 13x9x2-inch baking pan or 3-quart shallow casserole or spray with nonstick cooking spray.
In a saucepan over medium heat, melt the remaining 5 tablespoons of butter. Stir in the flour and cook, stirring, for 1 minute, or until bubbly and smooth. Gradually stir in the milk, then stir in the salt, pepper, nutmeg, and cayenne. Cook, stirring, until thickened. Add the cheeses to the sauce and cook, stirring, until cheese has melted.
Combine the sauce with the cooked and drained macaroni. Spoon into the prepared baking dish and sprinkle with the buttery bread crumbs.
Bake for 25 to 30 minutes, until browned and bubbly.
Calories per serving: 596
Fat per serving: 30.4