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.