Remove green tops from leeks and wash the white parts in cold running water, pulling them apart to flush out all the sand. Drain and chop them. Melt butter in a deep saucepan, add leeks and cook slowly until they are soft but not brown, stir frequently. Add broth, bring to boil and add potatoes, salt and pepper. Cover and simmer about 1 hour.
Rub thru a fine sieve, cool and then chill. Add cream and beat briskly with a wire whip. Strain again and add seasoning if needed.
Serve in chilled cups and sprinkle on top with chives. If desired, the strained puree may be kept in refrigerator for 2 or 3 days, and cream whipped in when the soup is ready to serve.
Yield: 10 to 12 cups.Makes 4 Source: