Macaroni& Cheese Casserole

1 package Macaroni & cheese -- prepared as directed

1 small onion -- chopped

1 pound ground beef

1 can Cream of Mushroom soup

1/2 cup milk

Brown beef and onion. Prepare macaroni & cheese. Add soup and milk to beef. Mix and warm. Combine both mixtures and stir or layer alternating soup mixture and macaroni.