1.Preheat the oven to 170ºC, gas mark 3, and line a 12-hole muffin tin with paper cases. Sift the sugar, flour, cocoa, baking powder, bicarbonate of soda and a pinch of salt into a large mixing bowl. Add the sunflower oil, eggs and soured cream and beat until smooth. Add 125ml boiling water and beat again to combine.
2.Divide evenly between the paper cases. Bake for 20-22 minutes until well risen and a skewer inserted into the centre comes out clean. Leave to cool for 5 minutes, then transfer to a wire rack to cool completely.
3.Meanwhile, roll the fondant into 12 even sized balls and press one M & M into each, to make eyeballs. Dip a wooden skewer or cocktail stick into the red food colouring and draw veins on each eyeball. Leave to dry.
4. For the buttercream, tip the sugar into a 2 litre heatproof mixing bowl or stand-mixer bowl. Add the egg whites, 2 tbsp cold water, vanilla and salt. Warm the bowl over a pan of simmering water – without the bowl touching the water. Using a balloon whisk, beat constantly for 5 minutes or until the sugar has dissolved, the meringue has doubled in volume, leaves a ribbon trail and is hot to the touch. Remove the bowl from the heat, and whisk with an electric mixer until the meringue is cold.
5.Gradually add the softened butter 1 tbsp at a time, whisking well between each addition. When all of the butter has been added the frosting may start to look a little curdled. If this is the case, continue to whisk and it will come back together. Add the green food paste or gel. Scoop the frosting into a piping bag fitted with a 4-5mm plain nozzle.
6.If the cupcakes have a very domed top, slice off a little to level it. Pipe the buttercream in a haphazard, wiggly fashion over the top of each to completely cover them. Top with a fondant eyeball and serve
Recipe and image courtesy of Waitrose & Partners