1 onion
1/2 c. chopped celery
1/2 c. chopped green pepper
2 lbs. ground beef
1/2 c. catsup
1 sm. jar Cheese Whiz

Saute first three ingredients in 1/2 stick butter. Add ground beef and brown. Add catsup and Cheese Whiz. Let stand overnight. Spread 1/2 bun with butter. Spread 1/2 bun with mustard. Put filling into bun. Wrap in foil and heat at 275 degrees for 1 hour.