Potato Leek Soup

Makes about 4 cups, serving 2 generously.

the white and pale green part of two large leeks, split lengthwise,
washed well, and chopped
1 tablespoon unsalted butter
1 1/2 cups water
1 cup chicken broth
1 pound boiling potatoes
2 tablespoons minced fresh parsley leaves

In a large heavy saucepan cook the leeks in the butter with salt and pepper to taste, covered, over moderately low heat, stirring occasionally, for 8 to 10 minutes, or until they are softened but not browned. Add the water, the broth, and the potatoes, peeled and cut into 1/2 inch dice, and simmer the mixture, covered, for 20 minutes, or until the potatoes are tender. In a blender, puree 1 cup of the soup, stir the puree into the remaining soup with the parsley, and season the soup with salt and pepper.