Product Recall: Kraft and Polly-O String Cheese and String Cheese Twists. Click here
HEAT grill to medium-high heat.
MIX meat, cheese mixture, onions and 1/4 cup ketchup just until blended; shape into 6 (1/2-inch-thick) patties.
GRILL 4 to 5 min. on each side or until done (160ºF).
SERVE in rolls, topped with remaining ketchup.