Wash the sweet potato thoroughly, peel it, boil until soft, and mash.
In a bowl, combine the mashed sweet potato, cake flour, baking powder, sugar, and salt.
Cut the butter into small pieces and mix it evenly into the dough.
Add milk while forming the dough into one lump.
Divide the dough into appropriate portions and shape into balls.
Line a baking tray with parchment paper and place the shaped dough on it.
Bake in a preheated oven at 180°C (356°F) for 20–25 minutes until golden brown.