Prepare the base recipe.
Take a large bunch of continental parsley and pick over it, losing the bigger stalks. Bring a large pan of water to a boil and blanch the parsley in this for 1 minute, then refresh by immersing in cold water. Add the cooked parsley to the soup and liquidise. Do not be too alarmed by the rather violent green colour of this soup. It is on the menu regularly at Frith Street with truffled crème fraîche.