1 sm. pkg. shell noodles
4 tbsp. butter
4 tbsp. flour
3 c. milk
2 1/2 c. American cheese, grated
1/4 c. onion, minced
1 tsp. prepared mustard
1 tsp. salt
1/4 tsp. pepper

Prepare shell noodles according to package directions. Drain. In medium saucepan melt butter. Add flour and cook stirring constantly for 2 minutes. Do not brown. Stir in milk, cheese, onion, mustard, salt and pepper. Cook until cheese is melted. Mix in shells. Pour into dish. Bake at 350 degrees for 30 minutes.