From: Pinch My Salt
3 tablespoons butter
3 leeks, thinly sliced
1 medium or large onion, chopped
6 – 8 russet potatoes, thinly sliced
3 1/2 cups chicken broth (or enough to barely cover potatoes)
1 cup heavy cream
salt to taste
fresh ground black pepper to taste
1) Melt butter in a large saucepan over medium heat then add onions and leeks. Cook, stirring, until onions are limp and just slightly brown.
2) Add sliced potatoes to saucepan then pour in enough chicken broth to just barely cover the potatoes. Continue cooking over medium heat until potatoes are tender. Using a potato masher, mash and stir potatoes until desired consistency is reached. As you mash the potatoes and the soup thickens, turn down heat and stir frequently with a large spoon to prevent scorching on the bottom.
3) Add one cup of heavy cream (or more if you desire) and salt and black pepper to taste. Cook 15 minutes more over low heat, stirring frequently, then remove from heat and serve.