2 quarts water
1 lb potato, peeled and diced
1 onion, finely chopped
1 cup sour cream or 1 cup plain yogurt
1 teaspoon flour
1 tablespoon chopped parsley
1 teaspoon butter
salt, to taste
1. Boil the cubed potatoes with the finely chopped onion.
2. When they are done, strain, reserving the cooking liquid.
3. Mash thoroughly or rice the potatoes and thin with enough of the cooking liquid to make a soup of the consistency you prefer.
4. Add salt to taste and bring back to the boil.
5. Mix the sour cream or yogurt with the flour. Add it to the soup, stirring constantly.
6. Let boil for a minute or two, add the chopped parsley and butter.
7. Serve with toast.