In a small frying pan heat the cumin seeds, coriander seeds, cinnamon stick, cloves and peppercorns over a high heat for about a minute.
Transfer the spices from the frying pan into a spice grinder and grind until smooth.
Add the ground spices and the remainder of the masala ingredients to a food processor and blend until smooth.
Mix the masala with the pork pieces and leave to marinate for at least a couple of hours and ideally overnight.
Add the oil to a heavy bottomed pot and saute the onions until golden brown. Add the marinated pork and marinade and cook for about 5 minutes. Add the chicken stock to the pan, turn down the heat and simmer for 40-45 minutes until the pork is tender.