Prepare waffle batter and use to prepare 12 waffles as directed on package.
Heat large skillet on medium heat. Meanwhile, fill waffles with all remaining ingredients except butter to make 6 sandwiches. Spread outsides of sandwiches with butter.
Add sandwiches, in batches, to skillet; cook 3 min. on each side or until Singles are melted and sandwiches are golden brown on both sides.