Pour the coconut milk into a cauldron, add sugar, tapioca starch, and agar powder, add vanilla beans to soften them.
Cook over medium heat until the sauce thickens slightly; remove from the heat.
Take out the vanilla pods, open them lengthwise with a sharp knife and scrape off the seeds (I will publish a demo video soon). Then, add the vanilla seeds to the cauldron.
Dip the empty vanilla pods into the sauce for a few seconds, remove and squeeze them well to ensure no seeds remain. If there are any seeds left, add them to the sauce and mix well.