3 lb lean ground beef
1 small onion, chopped
1 tablespoon Worcestershire sauce
1 tablespoon chili sauce
1 teaspoon salt
1/2 teaspoon black pepper
1/2 lb pepperjack cheese, divided into 6 chunks
6 hamburger buns, split
In large bowl, combine first 6 ingredients. Divide mixture into 6 portions; lightly shape each portion into a big 1/2-inch-thick patty. Remove some of the meat from the top center of each patty; insert a chunk of cheese (flatten chunk slightly with your palm to fit the hole). Replace meat over cheese.
Preheat grill to medium heat. Grill burgers 5 to 7 minutes per side. Serve on buns.