Wash the sweet potatoes thoroughly and boil them. Then peel the skins.
Mash the boiled sweet potatoes and mix them with sugar and butter.
Add eggs and milk, and mix well.
Sift in flour and baking powder, then knead to make the batter.
Pour the batter into a cake mold.
Bake in a 180°C oven for 30 to 40 minutes.
Let it cool, then cut into pieces for serving.