Prepare the leeks by using only the white part and chopping them.

Chop the onion and mince the garlic.

In a large pot, sauté the chopped leeks, chopped onion, and minced garlic in margarine over medium heat until translucent.

Add the chicken broth and the peeled and diced potatoes to the pot.

Bring the mixture to a boil, then reduce heat and simmer until the potatoes are tender.

Carefully puree the mixture in a blender in batches.

Return the pureed soup to the pot.

Add the whipping cream, salt, and pepper.

Heat the soup, stirring occasionally, until hot but not boiling.

Garnish as desired and serve.