Special equipment: 1 (12-cup) cupcake pan or 3 (12-cup) mini-cupcake pans with appropriately sized paper baking cups
Preheat the oven to 400 degrees F.
Put all the ingredients for the cupcakes except the milk into a food processor and blitz furiously. Then pour in the milk, and process again until you have a smooth batter. Divide the mixture between either the big muffin pans or the 3 small pans.
Cook the big cupcakes for about 15 to 20 minutes, and the small ones for about 10 minutes, although you might need to keep a closer eye on the little ones. Cool the cupcakes on a wire rack.
To ice the mini-cupcakes, mix the confectioners' sugar with a tablespoon or 2 of water from a recently boiled kettle or cold water (according to package instructions) for instant royal icing until you have a smooth, spreadable paste. In both cases add water slowly: you don't want this runny, and nothing is more irritating than having to start sifting more sugar. The merest, tiniest blob of food-coloring paste- in this case, as I said, Grape Violet - will be enough to bring a dizzy and rich-toned intensity to the proceedings; you can always add more coloring if you want, but again the important thing is to guard against having to do any more sifting. And if you have been too heavy-handed and landed yourself with a batch of unusable dark icing, then just make up some more plain white icing and add to tone down.
Slice any peaking humps off the tops of the cakes with a sharp knife and then pour, from a dunked-in spoon, the icing over each cake until the tops are thickly and smoothly covered. Let stand for a couple of minutes until the icing has set a tiny bit and then dot a gold button or other decoration of your choice on top.
Put both ingredients in a saucepan and, over low heat, cook until the chocolate's melted. Whisk together with handheld mixer or electric whisk (for ease and preference), watching the mixture become thick and glossy. Spoon and smooth over your waiting cupcakes. . Let stand for a couple of minutes until the icing has set a tiny bit and then decorate in whatever way you want.
Recipe courtesy of Nigella Lawson, 2007