Vichyssoise

For 4 people
1 large or 2 small leeks (white part only, finely chopped)
2 large potatoes, diced
1 large onion, chopped
2 tablespoons of oil
1 liter of vegetable stock
dried powdered Sage
8 tablespoons sour cream
salt
pepper
garlic powder

for the sour cream
soy yogurt

Saute for 3 minutes the leeks, potatoes and onion.
Add the stock, bring to a boil and cook over moderate heat until the potato is soft (about 20 minutes).
When cool, go to blender or blender and season with salt, pepper, sage and garlic powder.
Add the sour cream and stir gently; serve cold.
You can also use plain soy cream: the taste will be obviously different but the result equally agreeable.

Sour cream
After slightly salty, pour a jar of natural soy yogurt (preferably self produced, or at least no thickeners, otherwise the serum does not separate) in a strainer covered with gauze or cloth bag; leave it to drain in refrigerator (inside a container) for about 4 hours: there is a sour cream, to assemble if you want with olive oil to make it more uniform.
(Recipe taken and adapted from: http://www.kszm.org/wonderzdora/blog/_64 )