In a Dutch oven or skillet, heat up 1 - 2 tbsps oil over high heat. Once hot, stir fry ginger, garlic, and spring onion for 15 - 20 seconds until they release their fragrance.
Add cinnamon bark and star anise, and stir-fry for a few more seconds. Add water and bring to a boil.
Tip in the seasonings and gently put in the pork belly. Bring to a boil again.
Then reduce heat until the liquid is at a steady simmer. Braise for 2 - 2.5 hours, or until the pork is as tender as you'd like it. Note: If the liquid reduces too quickly before the pork is tender enough, add a bit more water as needed, and continue braising until the meat reaches the tenderness you want.
Dish out the pork and set aside to cool.
Cook the sauce
Strain the braising liquid into a small saucepan (discard the solids). If there isn't much liquid left, add 2 - 3 tbsps water and bring to a gentle simmer.
Sweeten with sugar and maltose (or honey), to your taste, to balance the saltiness of the soy bean paste.
Thicken with corn starch slurry until it has the consistency of a thick glaze. Note: If you added more water to the sauce, you may need to prepare extra slurry for thickening it.
Garnish and serve
Slice the braised pork into 2-cm thickness (or thinner, if you prefer). Arrange on a serving plate. Spoon the thick sauce all over and garnish with chopped spring onion or cilantro. Serve immediately.