Put the ginger, garlic, chilli powder, turmeric, salt, cardamom, cloves, peppercorns, cinnamon, coriander, cumin seeds and vinegar into a blender and blend to a puree. Scrape down the sides of the blender and blend for a further 30 seconds. Add more vinegar if necessary to form a smooth liquid paste.

Put the pork in a large bowl and pour over the spice paste. Cover and set aside to marinate for 1 hour. Lay the curry leaves, if you are using them, on top. Re-cover and put the bowl into the refrigerator for 24 hours, turning the meat two or three times during the period.

Two hours before cooking time, remove the bowl from refrigerator and set aside.

Heat the oil in a large saucepan. Add the mustard seeds and cover the pan. Fry the seeds until they pop, then add the pork, marinade and water and bring to the boil, stirring constantly. Reduce the heat to low, cover the pan and simmer for 30 minutes. Uncover and simmer for a further 30 minutes, or until the pork is cooked through and tender.

Transfer the vindaloo to a warmed serving dish and serve at once.