1. The plantains must be very ripe (soft and the peel dark). Place the plantains on the grill and cook them until, they are done, turning constantly. Once they are cooked, remove from the grill and peel. Return to the grill until lightly browned. Remove, cut lengthwise and top with butter and strips of cheese.
2. Return to the grill and cook until they are hot and the cheese starts to melt. Sprinkle with salt and serve hot.