Mashed Potato Soup

1/2 cup finely chopped onion
1 celery stalk, including the leaves, chopped fine
1 carrot, grated coarse
2 tablespoons unsalted butter
2 cups chicken broth
Pinch of crumbled dried rosemary
2 1/2 cups mashed potatoes
1 teaspoon white-wine vinegar
2 tablespoons snipped parsley leaves
Salt and freshly ground pepper

In a large saucepan cook the onion, celery, and carrot in butter over medium-low heat, stirring, until the vegetables are tender.
Stir in the broth and rosemary, and bring to boiling. Whisk in the potatoes, a little at a time, bring the soup to a boil again, stirring, and add the vinegar, parsley, and season with salt and pepper to taste.

Makes 4 servings.
--------

This is a great way to get rid of left-over mashed potatoes. This recipe can also be used to make a cream soup base. Just omit the rosemary, and add one cup of milk or cream after you add the potatoes. Let the soup simmer for about 15 minutes instead of bringing it to a boil after adding the milk.