baked macaroni and cheese

preheat oven to 400.

1 lb elbow mac
1/4 cup butter
1 small onion, minced
1/4 cup all-purpose flour
1/2 teaspoon dry mustard
1 1/2 teaspoons salt
pinch of pepper
3 cups milk
4 cups (16 oz) shredded cheddar cheese, divided
3/4 cup fine, dry breadcrumbs
2 T butter, melted

1) cook macaroni as directed
- I always try to under cook the macaroni a bit or the noodles get a bit mushy.
2) melt butter, add onion and cook a few minutes. add flour, mustard, salt, and pepper, stirring well. gradually add milk and cook, stirring constantly, until smooth and thoroughly heated.
3) add 3 cups of cheese to flour mixture and cook, stirring constantly, until melted. pour sauce over macaroni, tossing gently to coat well.
4) pour mixture into a buttered 2-qt baking dish. sprinkle w/ remaining 1 cup cheese.
5) combine breadcrumbs and melted butter, stirring well; sprinkle over cheese.
6) bake at 400 for 20 minutes. let stand a few minutes before serving.