Purple sweet potato powder was not available, so cocoa powder was used instead; the recipe may not be fully accurate.
Boil and mash the sweet potato.
Mix the glutinous rice flour and milk to make a dough.
Add the mashed sweet potato, sugar, and salt, then mix well.
Put the dough into muffin molds.
Bake in a preheated oven at 180°C for 25 minutes.