Preheat the oven to 200°C and fill a 12-bun muffin tray with paper cases.
Sift together the flour, baking powder bicarbonate of soda and sugar, divide between two bowls, then sift the cocoa powder into one bowl.
Mix all the liquid ingredients into a measuring jug, then divide equally between the two bowls. Mix together with a wooden spoon.
Spoon alternate spoonfuls of chocolate and plain cake mixture into the muffin cases. Bake for 20mins or until the cakes are risen and springy. Allow to cool.
Meanwhile, mix the icing sugar with a little water to make white icing, and cover the tops of the cakes. Allow to set. Press a chocolate button into the centre of each cake. Then use the writing icing to create eight 'legs' fanning out to the edge of the cases. If you use red writing icing, you can make bloodshot eyeball cakes instead!
Allow to set before serving.
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