Heat 2 tbsp oil in a large flameproof casserole and brown the pork in batches over a high heat. Return all the meat to the casserole, add the coriander and flour and cook for 1 minute, stirring.
Add the port and then the stock and seasoning and bring to a simmer. Cover and simmer for 1-1¼ hours until almost tender.
Meanwhile, heat the remaining oil in a large frying pan and cook the shallots over medium heat for 10 minutes or until lightly browned. Add the sugar and cook for a further 10 minutes until caramelised.
Add to the pork and simmer, uncovered for 15 minutes. Stir in the cranberries and chestnuts and simmer for a further 15 minutes until the meat and shallots are tender.