Have the butcher split the head and remove eyes, offal and brain. Wash in cold water, then put in a saucepan with peeled parsnips, 2 peeled onions, 2 peeled carrots, the green parts of the celery, the herbs, spices and seasoning. Cover with cold water, and bring to the boil, skim carefully. Cover and simmer for 2 hours. Sieve the meat and vegetables, reserving the liquid. Remove the bones, bring the liquid to the boil again. Add the barley and the rest of the carrots, onions and celery, nicely prepared and diced, and cook until tender. Meanwhile dice up all the meat from the head and trotter, and add to the pan. Arrange the meat and vegetables round the sides of a large mould, or two smaller ones, put the barley in the middle. Boil the stock until it is thick, and there is only enough left to fill the moulds. Pour in gently, and leave to set. There will be quite a thick film of fat on top, but do not remove this. Turn out and serve with salad.