Wash the sweet potatoes thoroughly, peel them, boil, and mash.
In a bowl, mix the mashed sweet potatoes, sugar, milk, and eggs evenly.
Sift the melted butter and cake flour into the dough and mix well.
Pour the batter into a cake pan and smooth out the surface.
Bake in a preheated oven at 180°C for 30 minutes.
After cooling, decorate with cream or nuts as desired.