Throw all the vegetables (onion, garlic, celery, leek, carrot, potatoes) into a large pot.
Heat the pot on medium heat and add a knob of butter.
Sweat the vegetables for a few minutes.
Add 1 liter of stock, cover the pot, and cook for 45 minutes.
Blend the soup until smooth.
Add a knob of butter and 150 ml of double cream, then blend one more time.
Season the soup with white pepper and salt.
Serve the soup with a dash of double cream and a sprinkle of parsley.
