Ingredients:

  Amount  Measure       Ingredient -- Preparation Method
--------  ------------  --------------------------------
                        -----fish stock-----
     1/4  cup           parsnips -- coarsely chopped
     1/2  cup           carrots -- coarsely chopped
   1      large         yellow onion -- coarsely
                        (3/4 cup)
   1      large         potato -- coarsely chopped
                        - 1 cup)
   1      teaspoon      salt
   6                    peppercorns -- whole
   1      tablespoon    parsley stems -- chopped
   1                    bay leaf
   3                    celery stalks w/leaves
   2      pounds        fish trimmings -- (heads, bones
                        washed)
   4      quarts        cold water
                        -----soup-----
     1/2  cup           carrots -- finely chopped
     1/4  cup           parsnips -- finely chopped
   1      pound         halibut -- cod or haddock,
                        -- boneless and in one
     1/2  cup           leeks; finely sliced -- white
                        only
   2                    egg yolks
                        salt and pepper
   3      tablespoons   parsley -- finely chopped
   6      tablespoons   sour cream -- (opt)

Preparation:

FISH STOCK: To prepare fish stock, which will be the base of the soup, combine the ingredients listed under that heading (above) in a 4 to 6 quart stock pot. Bring to a boil, partially cover the pot, turn the heat low and simmer for 30 to 40 minutes. Strain the stock through a fine sieve into a large bowl, pressing down hard on the vegetables and fish trimmings with the back of a spoon to extract their juices before discarding them. Wash the pot and return the strained stock to it. Reduce the stock to about 6 cups by boiling it rapidly, uncovered, for about 20 minutes. Restrain through a fine sieve or through a double thickness of cheesecloth lining a regular sieve. SOUP: Again return the stock to the pot. Add the carrots, parsnips and fish. As soon as the soup reaches the boil, lower the heat and simmer uncovered for about 10 minutes. Add the leeks and simmer 2 or 3 minutes longer. Remove from heat, lift out the fish with a slotted spoon and set aside on a platter. In a small bowl, beat egg yolks with a wire whisk; then beat in about 1/2 cup of hot soup, 1 tablespoon at a time. Pour this back into the soup in a thin stream, beating continuously with a wire whisk. With a fork, separate the fish into flakes and add it to the soup. Season with sale and pepper and reheat, but do not let the soup boil. To serve, ladle the soup into individual bowls and sprinkle with chopped parsley. If you like, garnish each serving with 1 tablespoon sour cream.