Pre soak red beans overnight or at least half a day. Transfer to a pot and discard the soaking liquid. Add around 1 liter clean water. Use high fire to bring to a boil and continue cook for another 10 minutes. Turn off the fire and cover the lid. Wait until the bean cool down. Restart the fire and continue cooking for 30 minutes over medium fire until the beans are completely soft. Add salt and sugar and give a big stir to mix evenly. Cool down and then refrigerated.
Peel the taro (ware gloves if you are sensitive) and cut into small chunks. If you are making sweet potato balls, peel them and cut into chunks too.
Set up the steamer and steam for around 15 to 20 minutes until a chopstick can insert easily. Set aside to cool down slightly.
In a large bowl, add around 100g tapioca starch and then throw the taro chunks in. Smash taro chunks with any familiar tool and then knead into a ball. If the ball looks really dry, you will need to add a small amount of water until the dough is well formed. Do not add a large amount once. I add 1 tablespoon each time.
Take one portion out and shape it into a really long thin log (1.5cm in diameter) and then cut into small portions. You need to be very careful in this step, as the dough is not as elastic as regular flour dough. You can start with a small amount each time.
Bring some water to boil in a pot, add taro balls in and continue cooking 1 minute after they floats on the surface (if you make purple sweet potato balls, remember to cook them last).
Add cooled red bean soup in serving bowls firstly and then top with taro balls, sweet potato balls; decorate with green peppermint and add ice cubes.