Preheat the oven to 200°C (top and bottom heat).
Melt the oil, butter, and powdered sugar over a pan of double boiler and then let it cool. Meanwhile, dissolve the cocoa powder in the hot water. Beat the eggs until light and fluffy. Carefully pour the oil-sugar mixture and flavorings into the eggs and stir in. Then stir in the dissolved cocoa. Finally, add the dry ingredients (flour, baking powder, and salt) and mix well.
The muffin batter can now be divided into the muffin cups and baked for 30-35 minutes. Allow the baked muffins to cool thoroughly on a wire rack.
For the blueberry frosting, first puree the blueberries. Then, using a mixer, mix them together with the remaining ingredients. The finished mixture can now be transferred to a piping bag and piped onto the muffins.
Now comes the fun part: Decorate the cupcakes for Halloween. For example, with jelly eyes or spiders, dough graves, and more. Let your creativity run wild and show us your results on social media!