In a large bowl, add in the egg, vanilla extract, and sugar. Use a hand mixer and mix until it turns light and pale in color.
Sift in the cake flour and baking powder. Mix with a whisk until combined.
Add in the milk and whisk until you have a smooth batter.
Set a little bit of the batter aside and dye it black. Transfer this batter into a piping bag.
Evenly divide the remaining batter into 4 cupcake molds.
Draw on the design on top of the cupcakes with the black batter.
Steam on medium heat for 20 minutes