Salt and freshly ground black pepper

Some leftover cooked boiled ham

Celery or lovage leaves

Drain and rinse the soaked ham hock and put it into a large saucepan along with the onion, celery, peppercorns, bay leaf, thyme and parsley stalks. Cover with cold water, bring to a boil and simmer, partially covered, for two to two and a half hours, until tender. Leave to cool in the liquid, then remove and strain the stock through a sieve into a bowl. Reserve the stock for making the soup, and shred the meat into bite-sized chunks. Taste the stock: if it''s too salty, let it down with a bit of water.

Rinse the soaked peas until the water runs clear (if you''re using lentils, pick over them and rinse).

Melt the butter in a large saucepan over a medium-low heat and sweat the onion until soft and translucent. Add the peas (or lentils) and the stock, bring to a boil, reduce the heat to a simmer and skim off any scum. Simmer until the peas (or lentils) are very soft, between 20-45 minutes. Blitz about three-quarters of the soup in a blender until smooth, adding a little more stock if it''s too thick. Season to taste. Return to the saucepan with the unblended soup, add some of the ham and warm through. Serve in warmed bowls, with some celery or lovage leaves scattered over the top.