This recipe combines the best of both worlds to bring two of America's favorite comfort food dishes, grilled cheese and scalloped potatoes, together for the ultimate gooey cheesy side dish.
Divide the potatoes and onions equally between two pieces of heavy-duty foil (about 18-inch squares) that have been coated with cooking spray.
Combine Parmigiano-Reggiano cheese and 3/4 cup each Cheddar and mozzarella; sprinkle over potatoes and onions. Top with bacon, butter, chives, all-purpose seasoning, and pepper.
Bring opposite ends of foil together over filling and fold down several times. Fold unsealed ends toward filling and crimp tightly.
Grill, covered, over medium heat for 35-40 minutes or until potatoes are tender.