Peel the taro, purple potato, and sweet potato separately. Then wrap each with tin foil, put in a steamer and steam for 15 minutes until cooked.Put purple potato, sweet potato, and taro in a fresh-keeping bag, and use a rolling pin to beat them into puree.Add some tapioca flour to the taro mash while it's hot. You can mix it with chopsticks at first, because it's wet and sticky. Add cassava flour several times, adding more flour each time it is completely out of dry flour. The amount of cassava flour is half of each ingredient, 200 grams of taro puree, and 100 grams of cassava flour. It may not be used or not enough. My mashed sweet potato used more than100 grams of tapioca flour, 90 grams of purple potato, and almost 100 grams of taro. Everyone comes according to actual operation, 100 grams is for reference only.Knead the purple potato puree, sweet potato puree, and taro puree into a ball, so that the dough does not stick to your hands and is flexible. If it feels wet, add a little tapioca flour or glutinous rice flour. If the puree is a little dry (such as purple sweet potato), you can add a little hot water while kneading it. Remember to add it in batches. Don't add too much at a time.Take a part of the mud and knead it into thin strips and cut into small pieces.Knead the taro balls and sprinkle some tapioca flour to prevent sticking.Boil a pot of water, add the taro balls for one serving, and gently scatter them with a spoon. The water boiled again, and the taro balls floated on the surface of the water. Cook for another minute and remove. The three colors can be cooked separately to avoid crossover. It’s okay for me to cook together here.Place the taro balls in cold water immediately. Spread the water three or four times until the taro balls are completely cool. In this way, the taste of taro balls will be more elastic.Boil a pot of water, with more water, pour the soaked sago into the boil, and cook on high heat for 15 minutes. Cook until there are only small white spots inside the sago, turn off the heat, cover and simmer for a while. If the sago is simmered for a while and it is not completely transparent, you can continue to boil, then cover and stew again, and repeat it twice to make sure it is completely transparent. Put the cooked sago into cold water. The sago tastes delicious.Take a small bowl, add sago and taro balls, pour milk, honey, and sprinkle some honey red beans on it. You can also cook the red bean soup and spoon into the taro balls, which is also delicious.