Cut banana peel lengthwise about 1/2 in. deep, leaving 1/2 in. at both ends. Open peel wider to form a pocket. Fill each with peanut butter and chocolate. Crimp and shape four pieces of heavy-duty foil (about 12 in. square) around bananas, forming boats.
Grill, covered, over medium heat for 5 minutes or until the chocolate melts. Top with crushed peanuts and cacoa nibs and enjoy.