Carefully remove the husks of each ear of corn, taking care not to rip the widest husks. Select the 24 widest husks and set aside, covered with damp paper towels. Cut 2 of the remaining husks into 8 long strips and reserve, covered with damp paper towels. Cut the corn kernels from each cob and reserve.
In a large bowl whisk together the lime juice, garlic, jalapeno, cumin and cayenne. Slowly add 6 tablespoons olive oil in a stream, whisking constantly. Add the corn, potatoes, black beans, red bell pepper and season with salt and pepper, tossing to combine and coat with the dressing. Taste and adjust seasoning if necessary. Add the cilantro leaves, stirring to combine.
Place 2 corn husks, concave side up, on a work surface, overlapping them at the wider ends by 2 inches. Center a third husk on top of the first two husks. Arrange about a 1/2 cup of the vegetable mixture in the center of the husks. Fold the sides of the corn husks up and over the filling to cover it completely. Tie at either end with a corn husk strip to secure the filling, forming a cigar-shaped packet. Make more packets in the same manner with the remaining ingredients. Packets can be made up to 4 hours in advance.
Preheat grill or grill pan.
Brush the packets with the remaining 2 tablespoons olive oil and grill each packet for 6 minutes per side, covered. If desired, cut each packet open and sprinkle grated cheese over vegetables. Return packets to grill or broil until cheese is melted. Serve immediately.
Recipe courtesy of Gourmet Magazine