În a large heavy sauce pan, melt the butter together with the olive oil and add the leek, potato and onion. Fry them a but until translucent. Than add the chicken stock and a bit of salt over the vegetables and bring it to a boil over high heat. Cover partially, reduce heat and simmer for 20 minutes until the vegetables are tender.

Correct the seasoning, to taste, and puree with a handheld immersion blender or in batches in a food processor.

Add in the heavy cream and reheat before serving. Enjoy it! Is delicious.