Ingredients:
1 medium leek
30 gm butter unsalted
350 gm potatoes, diced
80 ml chicken stock or water
1 medium carrot
1 medium turnip
110 ml crème fraiche or double cream
salt
white pepper
chervil leaves or parsley to garnish

Method:

1. Heat the butter in a large saucepan over medium heat.
   
2. Add the sliced white part of the leek and cook until soft but not coloured. Add potatoes and stock.
   
3. Season with salt and pepper.
4. Bring to the boil, reduce the heat, cover and simmer for about 30 minutes.
5. Put the carrots in a saucepan with enough cold salted to cover. Bring the bowl and cook for 1 minute. Add the turnip and cook for 2 minutes, then drain and set aside.
   
6. Refill the saucepan with salted water and bring to the boil. Add reserved green part of the leek and cook for 2 minutes, then drain and set aside.
   
7. Puree the potato and leek mixture in a blender or food processor. Strain extract of all liquid. Discard the solids. Return the soup to the saucepan.
   
8. Whisk the creme fraiche or double cream with a little of the hot soup in a small bowl. Return the mixture to the pan with the soup and heat gently to simmering point.
9. To serve, garnish with chervil leaves or parsley.