The original bisque was a crayfish purée, thickened with bread. Today, all kinds of shellfish are used and the soup is usually finished with fresh cream. The result is a rich and elegant soup.
Reserve 18 whole prawns for decoration. Roughly chop the remainder with the shells.
Heat the butter in a large pan and add the carrot, onion, celery and leek. Cover and cook over low heat until the vegetables are soft, but not coloured. Add the chopped prawns and their shells and cook gently for about 5 minutes. Add the brandy and boil, scraping the base of the pa