1In 10-inch nonstick skillet, cook beef, celery and onion over medium-high heat 5 to 7 minutes, stirring occasionally, until beef is thoroughly cooked; drain.
2Reduce heat to medium. Stir in salt, soup and mustard. Cook 10 to 15 minutes longer, stirring occasionally, until mixture is bubbly and vegetables are tender. Spoon mixture into buns.