Simple Macaroni and Cheese

Simple Mac and Cheese
1 lb Pasta cooked el dente
1 1/2 C. milk
2 T. flour
2-3 C. cheese
1/2 t. salt
1.4 t. powdered mustard

Warm 1 cup milk on low heat. Add flour to remaining 1/2 C. milk. When milk just begins to steam, add milk/flour mixture. Stir or low heat 3-4 min to slightly thicken. Add cheese, 1 cup at a time. When cheese is melted, add salt and mustard.  In a large bowl, combine cooked pasta with 1/2 of the sauce.  Stir and then add the remaining sauce. Serve while warm and creamy. If using as leftovers, add milk and warm on stove top to make creamy again.