Preheat the oven to 170C/340F/Gas 3.
For the pulled pork, oil a baking tray and place the pork shoulder on top. Mix together the chilli, mustard and salt and freshly ground black pepper, then rub the mixture into the pork shoulder.
Pour the vinegar and cider over, then scatter over the onion and garlic.
Cover with parchment paper, then wrap in foil and place into the oven to roast for three hours. Remove the parchment and foil, then roast for another hour.
'Pull' the pork by sticking a fork in the shoulder and shredding the meat into small pieces with another fork.
For the coleslaw, in a separate bowl, mix together all of the coleslaw ingredients until well combined.
To serve, pile the pulled pork shoulder on a serving plate and spoon the coleslaw next to it. Serve with soft white rolls and barbecue sauce to taste.