3 tbsp unsalted butter
6 medium leeks, chopped
6 potatoes, peeled and thinly sliced
6 cups Chicken broth
1 cup milk or cream
salt and pepper to taste
Add leeks to butter in a large saucepan and sauce , stirring, until tender, but not browned.
Stir in the potatoes and poultry stock. Bring to a boil, reduce heat, and simmer until the potatoes are soft, about 30 minutes.
Puree unit smooth, add milk and heat thoroughly, stirring until bubbles and then turn off heat. Season with salt and pepper to taste.