Start by heating a large skillet over medium heat.

Add the ground beef and cook until browned, breaking it up with a spatula as it cooks.

Stir in the chopped onion and bell pepper, cooking until softened, about 5 minutes.

Add the minced garlic and sauté for another minute.

Lower the heat and stir in the ketchup, Worcestershire sauce, brown sugar, and mustard.

Add salt and pepper to taste.

Let the mixture simmer for about 10 minutes, stirring occasionally.

While the filling simmers, toast the hamburger buns in a separate pan or under the broiler.

Once everything is ready, spoon the beef mixture onto the toasted buns.