Hot avocado and shrimp soup

1 small onion, diced    2 stalks celery, chopped fine
 4 cups chicken broth    1 bay leaf
 4 sprigs parsley        1 cup sour cream
 1/8 cup chopped chives  salt/pepper to taste
 2 medium avocados, peeled, seeded, roughly chopped
 1/2 cup cooked small shrimp, shelled, deveined
 Place onion, celery, broth, bay leaf, parsley, salt & pepper in a large
 saucepan. Simmer for 15 minutes. Strain and reserve stock. Place avocados in
 blender or food processor; puree avocados while slowly adding stock. When
 mixture is smooth, return to saucepan and heat gently; add shrimp. Cook over
 low heat until heated thoroughly, do not boil. Serve with a dollop of sour
 cream atop each serving, and sprinkle with chopped chives.