Butter heavily one side of a frozen hash brown pattie. Lay butter side down on a double strength sheet of aluminum foil. Top with a slice of American cheese, cover with sliced onions, top with 2nd slice of American cheese. Sprinkle with salt and pepper. Top cheese with another hash brown pattie, heavily buttered on one side, buttered side up. Seal with foil, making a packet. Grill on hot coals 20 minutes each side turning carefully so not to puncture foil. Serves 2.