Potage Belgique

I used to make this wonderful soup often. It's from San Francisco a la Carte, one of my favorite cookbooks. I'm hoping to make it over the Christmas holiday this year. 4 T butter 5 large leeks washed and thinly sliced 1/2 lb mushrooms thinly sliced 4 cups chicken stock salt and pepper 4 med. pot, peeled and diced 1 cup light cream chopped chives for garnish. Saute leeks and mushrooms in butter 5 min. Add chicken stock, salt and pepper. Add potatoes and simmer 30 min. Blend all in blender until smooth, adding cream. Garnish with cream.