- Bring everything except the cornstarch to a boil in a medium saucepan over medium heat.
- Boil until reduced by a third. Strain out the sauce into a bowl to remove the onion and star anise. Return the liquid to the pan and bring back up to a boil.
- Mix the cornstarch with a few tablespoons of water and then whisk into the sauce until thickened.
- Cool and serve with siopao or Filipino pulled pork.