Preheat the broiler or prepare a charcoal grill, with the rack adjusted so the peppers will be as close as possible to the heat. If using the broiler, place the peppers on a foil-lined baking sheet. Broil or grill the peppers, turning with tongs, until charred on all sides, 8 to 15 minutes total. Wrap the foil around the peppers, crimping the edges to seal shut (or place