Salt and fresh ground white pepper Whip cream (optional) Chop green onions, chives or parsley (garnish) Melt butter in heavy medium saucepan over low heat. Add leek, onion and celery and cook until soft but not brown. Stir occasionally, about 10 minutes. Add broth and simmer 10 minutes. Puree in batches in blender. Return to saucepan. Mix cream cheese and sour cream in processor until smooth. Add to soup and stir over low heat until heated through; do not boil. Season with salt and pepper. Thin with whipping cream if desired. Serve. Serves 8. Garnish with green onion, chives or parsley.