To prepare the pork, pierce the rind side of pork with a sharp fork or knife until the skin is covered with fine holes.
Bring a large pan of water to a boil and, using a large ladle, pour the hot water over the rind side of the pork several times. This is best done suspending the pork above the sink by a hook, but you can place it on a wire rack in the sink instead. Set the pork belly aside.
Heat a wok until it is hot, then add the salt, pepper, five-spice powder and sugar and stir-fry the mixture for 3 minutes. Allow the mixture to cool slightly.
When the mixture is cool enough to handle, rub it into the flesh side of the pork. Hang the meat to dry for 8 hours or overnight in a cool place or in front of a fan. Alternatively, place the meat on a wire rack set above a roasting tin.
To cook the pork, preheat the oven to 200C/180C fan/Gas 6.
Place the pork on a wire rack, rind-side up and roast for 20 minutes.
Reduce the heat to 180C/160C fan/Gas 4 and continue to roast for 2 hours. Turn the oven back up to 230C/210C fan/Gas 8 and cook for 15 minutes. Remove the meat from the oven and allow the pork to cool.
For the greens, heat a wok, once hot, add the ingredients and cook for 2-3 minutes.
To make the dressing, place all the ingredients into a pestle and mortar and pound to a rough paste.
To serve, stir the dressing through the wok vegetables and scatter on a large plate. Cut the pork into small squares and dot around the plate. Garnish with the spring onions and chilli.