Soften butter at room temperature and mix it with sugar until smooth.

Add the egg and vanilla extract in three separate additions, whipping each time.

Sift cake flour, baking powder, and cocoa powder, then mix them into the batter.

Fill a piping bag with the batter.

Prepare the pan by coating it with melted butter and flour, then pipe the batter into the pan.

Bake in a preheated oven at 180°C (356°F) for 20–25 minutes.

Let the Gugelhupf cool completely before decorating with the chocolate pen.

Sprinkle the Gugelhupf with sprinkles for added decoration.