Directions:

Slice leeks thinly; peel and slice potatoes. Cook leeks in butter until limp. Transfer them to a soup pot and add the potatoes. Add salt and stock; let simmer until potatoes are very tender.

Put contents of pot through a sieve; return mixture to soup pot and add milk. Let simmer a few minutes. Correct seasoning and add a little ground white pepper if you like. Chill in the refrigerator. Just before serving, beat in the cream. Serve in chilled bowls and sprinkle the top with chopped chives.