Peel and cut the sweet potato into small cubes. Soak the tapioca pearls in water until they expand. Peel the bananas, slice them lengthwise, and toss with a little sugar to let them absorb the sweetness.

Bring 2 cups cold water (about 480 ml) to a boil with the sugar, stirring until dissolved. Add the sweet potato cubes. Once the sweet potatoes have boiled for a few minutes, add the bananas and soaked tapioca pearls. When the tapioca pearls turn translucent and both the sweet potatoes and bananas are soft, it's ready. In a separate pan, heat the coconut milk with a little cornstarch and a pinch of salt until slightly thickened, then pour over the dessert. Sprinkle with toasted sesame seeds for extra flavor.