A great side to roasts and BBQ's, especially in a buffet line or at a dinner party. They can be made a day ahead and heated in the oven before serving. Any unused mashed potatoes can be put in a casserole and refrigerated up to 10 days. Simply reheat in the oven when needed. The recipe is intentionally vague about ingredient quantities other than the mashed potato stuffing. Make as many or as few onions as you need. You can make large, dinner-sized onions or tiny appetizer onions. Prep time and yield will vary accordingly.