First slice the sweet potatoes and put them in a pot for steaming, then add sugar while hot, mash the sweet potatoes and add them to the condensed milk. Add tapioca starch in several times. Be sure to add it while it is hot. You don’t need to add water. The hot sweet potato paste is easy to knead, and it will become hard when it cools. Knead the tapioca starch several times until it does not stick to your hands and make it look like you like. Mine is simple and rude. Sprinkle with dry powder, put the taro balls in the anti-sticking water, boil until they float and they are cooked. Then put them in cold water and soak for 2 minutes. Add coconut milk or milk. It's delicious.