In this recipe, created by firehouse chef Joe Bonnano, apple juice can be substituted for the liqueur, if desired. For a nonfat version, omit the butter and serve over nonfat frozen yogurt.
Build a charcoal fire in an outdoor grill, and let burn until coals are covered with white ash. Let the fire burn down to medium-hot (you should be able to hold your hand at grate level for 3 seconds). In a gas grill, preheat to medium.
Tear off six 12-inch squares of aluminum foil. Fold one foil square in half, and unfold. On the half below the fold, place 2 tablespoons brown sugar, 2 tablespoons Kahlua, 2 tablespoons butter, and 1 sliced banana. Sprinkle with cinnamon. Fold the foil over to form a packet, crimping the open edges to seal. Repeat with the remaining ingredients. (The packets can be prepared up to 1 hour ahead and kept at room temperature.)
Place packets on grill, and cook until sugar, Kahlua, and butter are boiling (open a packet to check), 5 to 7 minutes. Open the packets, pour over bowls of ice cream, and serve immediately.