1. Heat oil in a large soup pot over medium heat. Add onion and garlic, and cook 7 to 10 minutes or until tender. Stir in bay leaves and next 5 ingredients. Cook 2 minutes.
2. Stir in broth and next 3 ingredients. Bring to a boil, reduce heat, and simmer 30 minutes.
3. Stir in clams and white fish; cook 5 minutes. Stir in shrimp, crab, and squid, if desired. Cook 5 minutes or until seafood is opaque and clams open wide. (Discard any that do not.)
4. Ladle cioppino into bowls, and top with chopped parsley. Serve with sourdough bread.