Combine the hoisin sauce, soy sauce, sherry, sugar, ginger, garlic, Chinese five spice, cinnamon and star anise in a shallow bowl. Add the pork and turn to coat. Place in the fridge for 1 hour to marinate.
Preheat the oven to 140°C.
Transfer the pork mixture to a shallow roasting pan and arrange in a single layer. Cover with foil and roast for 2 hours, turning occasionally.
Remove the foil and roast the pork for a further 30 minutes, or until the sauce thickens and pork is very tender.
While the pork cooks, cook the choy sum and pak choy in a steamer over a saucepan of simmering water for 1 minutes or until they are bright green. Using tongs, quickly transfer the vegetables to a bowl and iced water to stop the cooking process.
Serve the pork on a large plate alongside the vegetables.
Recipe from pork.co.nz