Macaroni and Cheese for 25

2 pounds elbow macaroni
2 quarts milk
3/4 cup butter or margarine
1 cup all-purpose flour
1 tablespoon salt
1-1/2 teaspoons dry mustard
2 pounds (2 quarts) sharp Cheddar cheese, grated
1 medium onion, grated
2 teaspoons Worcestershire sauce

Directions:
About 1-1/2 hr. before serving: In large pot, cook macaroni as label directs; drain. Meanwhile in microwave, heat milk until very hot (do not boil). In large saucepan, melt butter. Stir in flour, salt, and mustard; cook for ten minutes, stirring often. Stir in heated milk; cook until thickened, stirring constantly. Add cheese, onion, and Worcestershire; stir gently until cheese is melted. Remove from heat; stir in macaroni.

Start heating oven to 400°. Pour macaroni into greased pan(s)and bake, uncovered, for 30 minutes. Let stand about 5 minutes before serving. Makes 25 servings.

Notes:
If you're feeling cheap, you can substitute Velveeta or a store-brand substitute for the cheddar. It will still be good, but it's better with cheddar. When using Velveeta, I decreased the milk to 6 cups and added 2 cans Campbells Nacho Cheese soup. This turned out good, and I had many requests for the recipe. Half a recipe will fill a 9x13" baking dish, or the full recipe will make two full 9x13" dishes.