1. In a heavy 6-quart saucepan or a soup kettle, simmer the potatoes, leeks, chicken stock and salt partially covered for 40 to 50 minutes or until the vegetables are tender.
2. Force the soup through a food mill or sieve into a mixing bowl and then pour back into the pan. Season the soup with salt and a few grindings of pepper, and stir in the cream. Before serving, return the soup to low heat and bring it to a simmer.
3. Ladle the soup into a tureen or individual soup bowls. Serve garnished with fresh chives or fresh parsley. Season and stir in 1˝ cups of heavy cream. (Do not use a blender; the mixture will be too smooth.) Chill the soup until it is very cold. Serve it garnished with finely cut fresh chives.
