In a large bowl, combine ground beef, salt, pepper, and onion; mix thoroughly. Shape into 12 equal patties. Reserve 1/3 cup shredded Wisconsin Pepper Jack cheese. Top six patties with remaining cheese, divided evenly. Place remaining patties over cheese-topped patties and firmly press edges together. Grill over high heat, 3 to 4 min. per side or until done. For the last two min., spoon 1 Tbsp. salsa on each burger and sprinkle with reserved cheese. Place each burger on a bun; serve immediately. Makes 6 servings.

   Additional ideas for topping and stuffing: Wisconsin Cheddar cheese and bacon, Wisconsin Blue cheese and sautéed red onion, Wisconsin Swiss cheese and mushrooms, Wisconsin Feta cheese and Kalamata olives, Wisconsin Smoked Provolone cheese and roasted red peppers.