Spray a 24-inch piece of heavy-duty foil with cooking spray.
Prepare your fire with either wood or charcoal. Let it burn down until ash gray with moderately hot coals but no big open flames.
Thinly slice the potatoes and place them in the middle of the foil. Add salt and pepper, to taste.
Thinly slice the butter and place it on top of potatoes.
Top potatoes with the bacon pieces and green onion.
Top everything with cheddar and mozzarella cheese.
Fold the foil up over the potatoes and fold in the edges to make a foil pack
Place over the fire or grill on medium heat and cook for 20 minutes, depending on the thickness of the potatoes.
