Preheat the oven to 180°C.
Sear the rolled pork neck over high heat until brown and caramelised.
Transfer the pork to a roasting pan, then surround it with onions, garlic, leeks, butter, red wine vinegar and olive oil.
Season with salt and green peppercorns, then roast for 45–60 minutes until the onions are caramelised and the pork is tender.
Blend the chopped parsley with chopped capers, the juice and zest of 2 lemons, 2 T olive oil and season to taste. Serve with the pork and mash or creamy polenta.