Preheat oven to 350 degrees F. Scrub the potatoes. Pat dry with paper towels. Bake potatoes for 45 minutes. Remove from oven and place on a cutting board. Let cool for 30 minutes. Slice each potato lengthwise, cutting off the top quarter. Scoop out the pulp to form the boat. Put the pulp into a large bowl and add sour cream, scallions, basil, tomatoes and rosemary. Mix together until you have a smooth texture. Stuff each potato with stuffing. Sprinkle with cheddar cheese and parsley. Place in covered barbecue and cook for another 15 minutes. Remove with barbecue tongs to serving tray and serve hot.