HEAT oven to 400ºF. Mix meat, cracker crumbs, Parmesan and 1/4 cup pasta sauce. Shape into 12 meatballs, using about 2 Tbsp. meat mixture for each.
PLACE, 2 inches apart, in shallow baking pan sprayed with cooking spray. Press 1 cheese cube deeply into centre of each meatball.
BAKE 14 min. or until meatballs are done (160ºF). Meanwhile, microwave remaining sauce in microwaveable bowl on HIGH 30 sec. or until heated through; spoon into buns. Fill with meatballs.