1 (16 oz) box pasta (I like shells, radiatore, penne, or rigatoni; you need something with holes to hold the sauce)
2 tablespoons butter or margarine
1/4 cup flour
1/2 teaspoon dry mustard
2 1/2 cups milk (I use skim, because its what's in the house; if I'm making this for company or to take to someone I use 2%)
2 cups cheese (although I always double it)
Parmesan Cheese, shredded or grated
Italian bread crumbs
Salt and pepper to taste
Preheat oven to 375°F.
Grease a 9x13 pan or a 2 quart casserole dish, either works fine. Boil water for pasta, and cook following label directions. I usually wait until the water boils and then make the cheese sauce while the pasta cooks).
In a large saucepan, melt butter or margarine. Whisk in flour, mustard, salt and pepper. Over medium heat, whisk in milk gradually, and stir constantly until thickened. If you aren't sure if its thickened yet; its not. Be patient.
When milk mixture is thickened, remove from heat and stir in cheese until completely melted. Pour drained pasta into baking dish, add cheese sauce, and mix gently. Smooth top with the back of a spoon or a spatula, then sprinkle on a thin layer of Parmesan followed by a thin layer of bread crumbs. Bake for 25 minutes.