Preheat the oven to 180°C, fan 160°C, gas 4. Line a 6-hole muffin tin with paper cases.
Put the cocoa powder and 50ml boiling water in a small bowl and stir until smooth. In a separate bowl, lightly whisk the egg with 20ml water, then set aside.
In another bowl, sift together the flour and baking powder, then stir in the sugar. Add the cocoa mixture and the spread. Using an electric hand-held whisk, beat for 1 minute, then gradually add the egg mixture, whisking well after each addition.
Spoon the mixture into the paper cases, then bake for 25 minutes until cooked through. Transfer to a wire rack to cool completely.
Meanwhile, melt the chocolate in a heat-proof bowl over a pan of simmering water. Remove from the heat then slowly beat in the cream to make a thick, glossy ganache.
To decorate, put the cooled cakes back into the tin. Cut a point in one end of each cola straw and push 8 (pointed end first) into each cake as legs. Spread the ganache over the middle of each cake.
Add the halved chocolate buttons for eyes, then make pupils with dots of ganache. Position the eyes on top of the cupcakes, then put them in the fridge for 10 minutes to set.
For fairy cake perfection see our 'How to' video