Macaroni and Cheese

This is one of those homemade comfort foods from my childhood.  'Nuff said.

2 quarts water
Salt
1(8-ounce) package elbow macaroni
4 tablespoons butter or margarine
¾ cup fresh bread crumbs or saltine cracker crumbs
1 small onion, minced
1 tablespoon flour
¼ teaspoon dry mustard
⅛ teaspoon pepper
1 teaspoon salt
1½ cups milk
2 cups shredded Cheddar cheese

1. In a 3-quart saucepan, heat to boiling water and 1 teaspoon salt.  Add macaroni; cook until tender but firm; drain.  Grease 2-quart baking dish.  Preheat oven to 350°F.
2. In 1-quart saucepan over medium heat, melt 2 tablespoons butter or margarine; add bread or cracker crumbs and toss to coat; set aside. 
3. Meanwhile, in 2-quart saucepan over medium heat, melt remaining butter; add onion and cook until tender, about 5 minutes.
4. Blend in flour, mustard, pepper and salt.  Stir in milk; cook, stirring, until thickened.  Remove from heat; stir in cheese.
5. Mix sauce with macaroni and pour into baking dish.
6. Sprinkle crumb mixture over top.  Bake in over 20 - 25 minutes.