1 1/2 pounds ground beef
1 small onion, finely chopped
1/2 teaspoon salt
1/4 teaspoon black pepper
1 tablespoon Worcestershire sauce
1/2 cup beef broth
1 package (12 count) slider buns
1 1/2 cups shredded cheddar cheese
1/4 cup butter, melted
1 tablespoon sesame seeds