Melt the margarine in a thick bottomed pan.
Add the peeled and washed sliced onion and leek , cook for a few minutes without color with a lid on.
Add the stock and the peeled, washed, sliced potatoes and the garni and season.
Simmer for approx. 30 min.
Remove the garni and skim.
Pass the soup firmly through a sieve then pass through a medium strainer.
Return to a clean pan, reboil, correct the seasoning and consistency.
Finish with cream and garnish with chopped chives, raw or cooked in a little butter.
Chill and serve.