*Note: The recipe calls for 1-2 chicken livers, if available, and "shreds of cold cooked chicken meat, if available". Grate the zest of the lemon very finely and reserve it. Put the barley into a soup pan, add 1 tablespoon lemon juice and cold chicken stock. Bring to the boil, cover and simmer for about 40 minutes until the barley is tender with just a hint of bite to the centre of the grain. Add the chicken meat, if used, to the pan towards the end of this time to heat it through gently but thoroughly. When the barley is nearly ready, slice the mushrooms thickly, and slice the leeks (tender green parts as well as the white) very thinly indeed so that the leaves fall into ribbony shreds. Cut the chicken livers, if available, into 2 to 3 pieces and saute them briefly in the butter until crusty on the outside but still pink within. Fry the mushrooms in the fat remaining in the pan then reduce the heat and cook the leeks gently for 2 to 3 minutes, just shaking occasionally. Then add contents of the frying pan to the soup pan. Add the mushrooms and check seasoning. Put the chicken livers into a warmed soup tureen and crush with a fork to make a coarse paste. Add the finely chopped garlic, the lemon zest and most of the parsley. Pour on the piping hot soup, stir to mix well, sprinkle the rest of the parsley on top and serve. Note: If the soup is not served straight away, but allowed to get cold, the barley will go on swelling and softening; when reaheated the dish then seems more like a stew than a soup. I like it this way but you may prefer to lift out the grain and cool it down separately from the rest of the soup.