1/4 cup butter OR margarine
1 Tbls. minced onion
1/4 cup all-purpose flour
2 cups milk
4 oz. process American cheese food (Velveeta®) – cubed
1/4 cup shredded cheddar cheese
2 Tbls. bleu cheese crumbles
1 tsp. salt
1 dash black pepper
1/4 tsp. ground mustard
1/4 lb. rotini pasta – cooked al dente
Cook onions in butter until transparent. Stir in flour and cook 2 minutes. Slowly stir in the milk. Stir in the cheeses, salt, pepper, and mustard. Continue to cook over medium heat, stirring constantly, until thickened. Stir in prepared pasta.
Lightly butter a casserole dish and pour pasta mixture to dish. Bake in a 400 degree oven for 20 minutes.