Heat a skillet over medium heat
Add 1 pound ground beef
Cook until browned, breaking it apart
Drain excess fat
Add 1 small chopped onion
Cook until softened
Stir in 1 cup ketchup
Add 1 tablespoon brown sugar
Add 1 tablespoon Worcestershire sauce
Add 1 teaspoon mustard
Add salt and pepper to taste
Simmer for 5 to 10 minutes
Spoon mixture onto hamburger buns
Serve warm