The "Leek & Potato Soup" recipe is a good example in utilizing potato to thicken soup, as compared to the traditional way of using "equal amount of butter & flour" as "roux" to make cream soup. It is healthier & heartier in my opinion.

BASIC CHICKEN STOCK:

1-2 lb. chicken parts, or thighs and legs, blanched in boiling water, skin removed, or the carcass of 1 cooked chicken

1 large onion, quartered                                              

2 stalks celery, chopped coarsely

2 carrots, cut into large pieces                                     

bouquet garni: tied in several layers of cheesecloth--optional

   

    1 bay leaf                                                   

    4 white peppercorns

    1 onion, stuck with 4 cloves

10-12 cups water

Put all ingredients in a large stock pot.  Bring to a boil, reduce heat and simmer for 3 hours. Strain and cool. Remove as much oil from the surface if possible. Stock may be made in advance & freeze until needed. Remove solid fat & defrost in the fridge.

Recipe may be doubled or tripled for larger quantity of stock.

LEEK & POTATO SOUP:

3-4 large leeks

2-3 tbsp. butter or oil

                                                                                   

3-4 medium potatoes, diced or thinly sliced

2 tbsp. finely chopped onion                                                  

8-10 cups of chicken stock

1/8 tsp. pepper + salt to taste                                       

2 cups milk (or 1½ C milk + ½ cup half and half cream)                    

chopped parsley to garnish

To prepare leeks:  Leeks are usually very muddy or sandy between the layers, so trim away all but the white and the tender light-green parts and cut off the roots. Strip off the coarse outer leaves and split the leek from about ½-inch from the bottom up. Leaving the bottom uncut will make it easier to slice the leeks later. Soak in cold water for 10 minutes and wash between the leaves under running water. Slice into 1/4-inch slices.

In a large pot, melt butter or heat oil over medium heat. Add leeks and onion. Cook until tender, but not browned. Add potatoes & stir together to cook for a few minutes. Add chicken stock, cover pot & turn heat to high, to bring to a boil. Then, reduce heat to medium-low & and simmer soup for 20 minutes. Add milk or milk mixture & bring soup to a boil, without covering pot to avoid boiling over. Cook 5-10 minutes more, or until vegetables are tender. Add seasoning to taste. Soup can be served like that, or if a creamy soup is preferred, use a hand blender to blend soup before serving. 

Ladle soup into heated serving bowls. Sprinkle each serving lightly with parsley to garnish.  

****This recipe can be adopted for other creamy vegetable soup. Just adjust the amount of potato or even sweet potato to the portion of other vegetables to be used, & blend soup before serving. But sweet potato will impart more sweetness to the soup, so it is a matter of taste****.