Creamy Chinese Celery Soup

Ingredients:
1 medium leek, chopped
1 medium potato
1/2 cup chopped Ishikuru onion
2 tbs unsalted butter
1 tbs olive oil
2 bunches Chinese celery, top leaves discarded and stalks cut into 4cm  pieces
1/2 cup dry white wine
4 cups chicken stock
1/2 cup cream
1/2 tsp salt
1/4 tsp black pepper
Chinese parsley leaves or flat-leaf parsley

Method:

1. Wash leek well in a bowl of cold water, then lift out and drain well. Peel and chop potato.
2. Cook onion in butter and oil in heavy saucepan over moderate heat, stirring until softened for about 2 minutes.
3. Add leek and cook, stirring until softened for about 5 minutes.
4. Add celery and potato and cook for 2 minutes.
5. Add wine and boil for 1 minute.
6. Add chicken stock and simmer, covered, until celery is very tender; about 1 hour.
7. Purée soup in batches in a blender until very smooth then pour through a large medium-mesh sieve into a bowl.
8. Transfer the soup to cleaned saucepan then stir in cream, salt and pepper and heat over low heat until hot.
9. Thin with water if desired.  Garnish with parsley.