Heat the oil in a large stockpot over medium heat. Add the prosciutto, and sauté for 2 minutes. Add the onion, celery, carrot, and garlic; sauté for 2 minutes or until soft.
Add the water, beans, bay leaves, and broth, and bring soup to a boil. Partially cover, reduce heat, and simmer soup for 20 minutes.
Add the parsley, sherry, and black pepper; cook for 1 minute. Discard bay leaves.