Mix together ground beef, sausage meat, bread crumbs, onion, tomato paste, egg, salt and pepper. Divide into 4 portions and shape into 1/2-inch patties.
Preheat grill to medium-high heat; grease grate well. Grill patties for 6 to 8 minutes per side or until grill-marked and cooked through. Top each patty with cheese and cook for about 1 minute or until cheese starts to melt.
Meanwhile, grill pancetta for 3 to 4 minutes or until golden and crispy. Grill buns for about 1 minute or until toasted. Assemble burgers in buns with lettuce, tomato and pancetta.
Tip: Serve with classic burger condiments such as ketchup, mayonnaise and hot mustard.