Baked Mac 'N Cheese

2 teaspoons butter
1/2 teaspoon salt
1/4 teaspoon pepper
3 cups milk
1/2 cup all-purpose flour
1/2 teaspoon dry mustard
1 1/2 cup cheddar cheese, grated
5 cups cooked elbow macaroni

In sauce pan, melt butter. Add flour, mustard, salt, and pepper. Cook 1 minute, stirring. Gradually stir in milk. Cook over medium heat until thick, 10 minutes, stirring. Stir in 1 cup cheese until melted. Place cooked elbow macaroni in two-quart dish, pour sauce over macaroni, and sprinkle with remaining cheese. Cover and bake at 350°F for 30 minutes.