Recipe: Gran's Potato Soup

My grandmother ("Gran") makes my favorite Potato Soup. A while back I grilled her for the recipe, and she finally shared it with me. Here it is:

Ingredients:

6-8 Potatoes, chopped into small cubes about 1/4 inch each
1 small Onion, chopped finely
1 stalk Celery, chopped finely
Water
1 large can of Evaporated Milk
Salt and Pepper, to taste
1/2 stick Butter or Margarine

Steps:

1. Boil the potatoes, onion, and celery in enough water to cover them.
2. When the potatoes are done, mash them slightly, using a spoon or other implement.
   This will thicken the soup somewhat.
3. Add the can of evaporated milk and the margarine/butter.
4. Add salt and pepper to taste. (I use about a teaspoon of salt and a quarter of a teaspoon of
   pepper.)