Cream of Potato Soup

Put the potatoes in the large (11 qt) soup pot. Add the onions to the potatoes. Cover potatoes with water and boil until tender. Watch while cooking, you may have to add glass or two of water if too thick. Do not pour off water when potatoes are done. Mash the potatoes. Add the diced ham and the butter. Let soup cool for one hour. Add the milk, stirring with masher as you are adding milk. Finally, using a "double boiler" bring the soup to serving temperature.