1. Preheat the oven to 180°C, gas mark 4.
2. Mix the sugar, 5 spice, soy and chilli oil in a bowl, add the pork and marinate for at least 1 hour. Transfer to a small roasting tin with the marinade and cook for 45 minutes. Turn the pork over, cover with foil and bake for a further 30 minutes. Allow to cool slightly before shredding the meat. Mix it into the juices with the hoisin.
3. Meanwhile, make the buns. Place the flours, salt and lard in the bowl of a stand mixer and blend until the lard has been rubbed in. Mix in the sugar and yeast. Heat the milk to just below boiling and add to the flour mix, then blend to form a dough. Knead in the mixer using a dough hook for 3-4 minutes. Transfer to an oiled bowl, cover with clingfilm and leave in a warm place for 1 hour or until risen slightly.
4. Sprinkle the baking powder over the dough and knead in. Divide into 12 balls, cover and leave in a warm place for 30 minutes.
5. Gently roll out each ball to a rough 10x7cm oval, brush with oil and fold in half, placing each on a small piece of baking parchment. Cover and leave for 30 minutes.
6. Place the buns and their parchment in a steamer and steam in batches for 8 minutes. Remove the paper and fill with the shredded hoisin pork.