1 lb. ground beef
1 med. onion, chopped
1 tbsp. flour
3/4 c. hot water
6 buns, split and toasted
1 1/2 tbsp. prepared mustard
3/4 c. chili sauce or catsup with chili powder

Brown beef and onion in a skillet; stir in flour and hot water. Cook for 5 minutes, stirring constantly. Add mustard and chili sauce and simmer for 15 minutes. Serve on buns.