Nose-to-tail eating is a hot topic these days, and brawn is a perfect example of it. The pigs head has a surprising amount of meat in it, and you also get lots of skin, fat and jellied stock to use in other dishes. Pigs heads are also amazingly cheap.
Unless you have a seriously big pan, an industrial bandsaw, or a big chopper and a good aim, you should ask the butcher to cut the head up for you. I find that 4 pieces is workable.
Pop the head portions into a big pan (if you can't manage to fit it comfortably into one pan, use two and split the ingredients between them). Add enough water to cover the head with about 2cm (1 inch) extra. Quarter the onions - leave the skin on - top and tail the celery and carrots, cut them into big chunks and add the vegetables to the pan.
Add the peppercorns and 2 teaspoons of the parsley, and bring to the boil. Skim off any scum that rises to the surface. Turn down the heat, pop a lid on the pan and simmer for 3 hours. Allow to cool enough for you to be able to remove the pieces of pigs head from the pan. Put them into a large bowl and stick them in the fridge to cool completely. Drain the liquid from the vegatables and boil rapidly until the volume of liquid is reduced by about half. Add salt to taste, and put it in the fridge.
Line a loaf tin with two layers of plastic film. Take the pigs head pieces from the fridge and pick off all the meat. Chop or tear the meat into smal chunks, combine it with enough stock to get everything coated, mix in the remaining parsley and pack it into the loaf tin. Pour extra stock over the top to fill in any gaps. Wrap the flim over the whole thing and leave to set for a couple of hours. When it has set, slice it and eat with toast, in a sandwich, or with a salad.