Boil potato, cool and set aside. May be refrigerated. Saute bacon (diced) with two of the diced onions until tender but not brown. Add vinegar, water, sugar and salt. Cook with cornstarch until consistency of heavy gravy. Pour over cooled sliced potatoes which have been seasoned with salt and pepper, Cool. Warm when ready to serve in oven, slow cooker or electric roaster. Add remaining raw onion to potatoes if desired. If potatoes seem dry add 1/2 cup salad oil, and mix up. After it is ready, it sits in the fridge over night, and is warmed up in a slow cooker and served warm. Hope that this helps.