Chop Swiss Chard and set aside.
Heat Butter in large pot over medium heat.
Add Celery, Swiss Chard, Onion, Carrots and Leeks and saute until wilted.
Add Potatoes and Stock then cover and simmer until Vegetables are tender.
Put aside Soup and add Cream and seasonings to taste.
Reheat but do not boil.
Serve with Sour Cream and chopped Parsley