7 tablespoons unsalted butter
1/4 cup plus 2 tablespoons all-purpose flour
4 cups milk
1 1/2 teaspoons dry mustard
1/8 teaspoons cayenne, or more to taste
1 pound macaroni
3 cups coarsely grated extra sharp cheddar (about 12 ounces)
1 1/2 cups freshly grated Parmesan chesse (about 4 ounces)
1 cup fresh bread crumbs
Heat oven to 350. Butter a 3- to 4-cup gratin dish or other shallow baking dish.
In a heavy saucepan, melt 6 tablespoons butter over moderately low heat. Add flour and cook rouz, whisking, three minutes. Add milk in a stream, whisking, and bring to boil, whisking continuously.
Add mustard, cayenne, and salt and pepper to taste and simmer sauce, whisking occasionally, until thickened, about 2 minutes.
Cook macaroni in salted water until just al dente, about 7 minutes. Drain well.
In a large bowl, stir together macaroni, sauce, Cheddar, and 1 cup Parmesan and transfer to prepared dish.
In a small bowl, stir together bread crumbs and remaining 1/3 cup Parmesan and sprinkle evenly over macaroni. cut remaining tablespoon butter into bits and scatter over topping.
Bake macaoni in middle of oven 25-30 minutes or until golden and bubbling.
Easy potluck item.