6 hamburger buns, split and buttered
1 lb. ground beef
1 (10 3/4 oz.) can condensed tomato soup
1 tbsp. mustard
1/2 tsp. salt

Heat oven to 325 degrees. Wrap hamburger buns in aluminum foil; heat in oven 15 minutes. In medium skillet, cook and stir meat until brown. Stir in remaining ingredients. Simmer occasionally. Spoon into warm buns.