4 tbsp butter or margarine
3/4 cup plain bread crumbs
1 small onion, minced
1 tbsp flour
1/4 tsp dry mustard
1/8 tsp pepper
1 1/2 cups milk
2 cups shredded cheddar cheese
Cook macaroni to package directions, drain. Grease 2-quart baking dish.
In a saucepan, melt 2 tbsp butter. Add bread crumbs and toss to coat. Set aside.
In another saucepan, melt remaining butter. Add onion and cook until tender. Blend in flour, mustard, pepper, and 1 tsp salt. Stir in milk, stirring until thickened.
Remove from heat, stir in cheese.
Place cooked macaroni in baking dish. Pour cheese sauce over macaroni. Sprinkle crumb mixture over top.