Make a Taiwanese snack favorite, sweet potato balls. They’re made with sweet potato and tapioca starch, rolled into balls and deep-fried until golden brown Steam the sweet potato in a steamer over a medium heat for 15-20 mins until soft enough to insert a cutlery knife into. Mash the sweet potato using a potato masher or a fork until smooth. Add the sugar, tapioca starch and a good pinch of seasoning, then mix well with your hands. Gradually pour in 1-2 tbsp. water, then mix well until a pliable dough forms. Divide the dough into four and roll each piece into a long sausage shape around 2cm in diameter. Cut each length of dough into 2cm pieces and roll them into balls in the palm of your hand. Don’t worry if they crumble, just keep squishing them until they form a ball. Half-fill a large, heavy-based saucepan with the oil. Heat over a medium temperature until a cooking thermometer reads 120C. Lower batches of the balls into the oil (you may need to cook them in two or three batches) and fry for 2 mins until they begin to float. When they are floating, turn down the heat slightly. Turn the balls in the oil using a slotted spoon until they expand in size, doing so every minute, for around 3-4 mins. Turn the heat back up and continue to deep-fry until golden brown.
Transfer the balls onto kitchen paper using a slotted spoon. Leave to drain and cool a little, then serve.