The next day, place the gammon in a large saucepan along with the onion, celery, peppercorns, bay leaf, thyme and parsley stalks.
Cover with the cold water and bring to the boil. Reduce the heat and simmer, partially covered, for two hours, or until the meat is cooked through.
Leave the gammon to cool in the liquid, then remove it and place on a chopping board.
Strain the stock through the sieve into the large mixing bowl. Set aside.
Shred the meat into bite-sized chunks.
Place the soaked peas in the sieve and rinse under cold water until the water runs clear.
Heat the oil in a saucepan and add the onions. Sauté until transparent.
Add the peas, half the gammon and the stock and bring to the boil.
Simmer for half an hour until the peas are soft.
Remove from the heat and use a stick blender until you have a smooth, thick soup.
Season to taste and stir in the remaining chopped ham.
Serve in bowls scattered with chopped parsley.
