Preheat the oven to 160°C.
Pour ginger beer into a medium roasting dish and add the onion, star anise, cinnamon stick and pork belly, fat side up (it should be submerged). Cover with foil and cook for 2½ hours.
Remove from oven and strain off 1 cup cooking liquid into a small pan. Add char siu sauce to pan and simmer for 3-4 minutes to make a glossy glaze.
Discard any remaining liquid, onion and spices from dish. Cut pork into strips or cubes, return to roasting dish and brush generously with glaze. Turn oven to 180°C and cook pork for 15 minutes or until caramelised and bubbling.
For the salad, layer the greens, pawpaw, and mint in a large serving bowl then scatter over coconut and peanuts. Combine sesame oil, lime juice, zest and chilli sauce in a jar and shake well. Drizzle over the salad at the last minute.
Serve the caramelised pork with the salad, drained, marinated onions and a lime wedge for squeezing.