Mince 3 medium leeks and 1 medium onion. Sautee in 2 tbs of butter for a few minutes until tender.
Peel and chop 4 medium potatoes (the smaller the pieces the better). Add the potatoes and 4 cups of chicken stock to the pot, and simmer until everything is tender (about 15 min or so). Put the entire mixture through a blender or food processor, then return to the same pot.
Add 1 or 2 cups of cream (depending on how creamy you want the soup), season with salt and pepper. On low heat reduce the soup to a creamy consistency - like creamy tomato soup, but not as thick as pea soup.