I had always thought that American cupcakes were the same recipe as the fairy cakes; (4oz each butter, sugar, flour+ 2 eggs), but the recipe is completely different. heavy on the sugar and low on the fat plus a load of milk, the method is different as well.
(recipe amounts halved from book)
4½oz/120g plain flour
5oz/140g caster sugar
1½ tsp baking powder
A pinch of salt
1½oz/40g unsalted butter, at room temperature
4½floz/120ml whole milk
¼ tsp vanilla extract
1 quantity vanilla frosting(9oz/250g icing sugar,3oz/80g butter1fl oz/25ml whole milk, few drops vanilla extract)
Hundreds and thousands or other edible sprinkles, to decorate
A 12-hole cupcake tray, lined with paper cases
Preheat the oven to 170C/325F/gas mark 3.
Put flour, sugar, baking powder, salt and butter in mixer with a paddle (or use a hand-held electric whisk) and beat on slow until you get a sandy consistency.Gradually pour in half the milk and beat until the milk is just incorporated.
Whisk the egg, vanilla and remaining milk in a separate bowl, then pour into flour mixture and beat until the mixture is smooth. Do not overmix.
Spoon mixture into cases until two-thirds full and bake 20–25 minutes,until light golden and the sponge bounces back when touched.
Beat icing sugar and butter together until well mixed. Combine milk and vanilla in separate bowl, then add to butter mixture a couple of tablespoons at a time. Once all the milk has been incorporated beat until light and fluffy, at least 5 minutes. The longer the frosting is beaten, the fluffier and lighter it becomes.
(From: Cake Days)