First make the masala marinade. With a pestle and mortar, coarsely crush together the cinnamon (or cassia bark) and cloves. Gently toast this mixture in a dry frying pan over a low heat until a spicy fragrance emanates from the pan. Tear the red chillies into pieces and add to the pan. Continue to dry-fry the mixture for a short while but do not burn. Set aside to cool.
Put the cooled spice mixture in a blender. Add all of the remaining masala ingredients and blend the mixture to a relatively fine paste. Taste and adjust seasoning if you like.
Rub the masala all over the pork, and place the meat in a dish in which it fits snugly. Set aside any remaining masala. Cover the meat and set aside in the refrigerator, if possible for a few hours.
Preheat the oven to 180C/350F/Gas 4. Pour the oil into a roasting tin and heat on the hob over a medium heat. Scrape any excess masala from the marinated pork, place the pork in the roasting tin and brown well on all sides. Transfer to the oven and cook for 30 minutes.
Reduce the oven heat to minimum. (You can now pour a few tablespoons of marinade over the pork for extra flavour. Any leftover marinade can be set aside to use for another dish.) Cover the pork tightly with aluminium foil, well tucked in so that the pork steams in the tin and the meat literally falls off when cooked. Cook for a further 3–3½ hours if using a rolled joint, although it may take as long as five hours. If you have the time, the meat will pull apart beautifully after 10 hours of cooking on a low temperature. If using smaller pieces or individual chops, adjust your cooking time accordingly.
Remove the pork from the oven and shred using two forks.
To serve, put some pork on top of a lettuce leaf. Top with some coleslaw and/or some coriander.