For the cocoa muffins, using a hand mixer, beat the butter with the eggs until fluffy. Stir in the vanilla sugar and sugar until a creamy mixture is formed.
Preheat the oven to 180°C.
Mix the flour with baking powder and cornflour and add to the butter-egg mixture until a smooth dough is formed. Stir in the persimmon powder until the batter is the desired color.
Prepare the muffin cups on a baking sheet lined with parchment paper. Divide the mixture evenly among the muffin cups and bake in the oven for about 25 minutes.
Let the cocoa muffins cool and serve.