Mash 1 cup potato pulp with a potato masher (save remaining pulp for a later use). Stir in sour cream, cheeses, tomatoes, green onions and parsley. Mixture should be sticky and hold together. With your hands, divide the mixture evenly between the potato skins, pressing the mixture into the skins. Sprinkle with fresh ground black pepper and bake for 15 minutes. Serve warm.