Photograph: Jonathan Gregson
Preheat the oven to 200°C, fan 180°C, gas 6. Make deep slashes over the pork and transfer to a large non-metal bowl or casserole. Put the garlic, ginger, paprika, chipotle paste, coriander, 1 tablespoon sea salt and 2 teaspoons black pepper in a mini processor with 3 tablespoons of the white condiment. Whiz to a purée and mix with the rest of the condiment. Rub into the slashes in the pork. Cover and set aside for at least 30 minutes.
Transfer the pork to a large, deep roasting tin and add 500ml of water. Cover tightly with two large overlapping pieces of foil. Cook for 30 minutes, lower the heat to 180°C, fan 160°C, gas 4, baste, cover and cook for 2½-3 hours until very tender.
To make a barbecue sauce, take the pork out of the tin and leave to rest on a board, covered in foil. Skim the fat from the juices. Pour the juices into a measuring jug, top up to 300ml with water, then pour into a medium pan, add the shallots and sugar and simmer for 15 minutes until slightly thickened. Strain into a serving bowl.
Light a barbecue and, when the coals are hot, rake to one side. Oil a rack, put it over the coals, throw the wood chips over the coals and sit the pork on the rack, on the opposite side, flesh-side down. Cover and leave to smoke for 10 minutes. Move the pork to a board and heat the buns. Shred the pork and pile into the buns with a slaw and some barbecue sauce.
Get ahead: marinate the pork a few hours ahead.
Kitchen secret: buy brioche buns if you can find them, their slight sweetness goes brilliantly with the spicy pork.