Line a muffin tin with paper cases. Sift the cocoa powder into a bowl, pour in the boiling water and mix into a thick paste. Add the remaining cake ingredients and mix with an electric hand whisk (or beat with a wooden spoon).

Divide the mixture equally between the 12 paper cases. Bake in a preheated oven at 200°C (400°F, Gas mark 6) for about 12-15 minutes until well risen and springy to the touch. Cool in the cases on a wire rack.

To make the chocolate icing melt the butter and pour it into a bowl. Sift in the cocoa powder and stir in the icing sugar a little at a time to make a glossy and spreadable. If the icing is too thick, gradually add the milk until it reaches the desired consistency. Pipe over the cupcakes, sprinkle with chocolate decorations and leave to set before serving.