Silky smooth frosting
1.Preheat the oven to 180°C (160°C fan-forced). Line 15 holes of two 12-hole (1/3 cup/80ml) muffin pans with the paper cases.
2.Beat the butter, extract and sugar in a small bowl with an electric mixer for about 5 minutes or until pale and creamy. Add the egg and colouring; beat until combined. Reduce the speed to low; add the combined sifted flour and cocoa, then the buttermilk in two batches.
3.Combine the vinegar and soda in a small bowl (the mixture will foam). Stir into the cake mixture.
4.Spoon about 2 tablespoons of the mixture evenly into paper cases. Bake for about 20 minutes or until cooked when tested. Transfer to wire racks to cool.
5.Meanwhile, to make silky smooth frosting, place the egg whites and sugar in the small heatproof bowl of an electric mixer. Place the bowl over a pan of simmering water. Whisk until the sugar dissolves and the egg whites are very warm to touch, about 70°C on a sweets thermometer. Beat on high speed for 5 minutes. With the motor operating, add the butter, a piece or two at a time. Beat until the mixture is smooth and creamy. Beat in extract or essence.
6.Pipe silky smooth frosting on the cakes with a plain tube or, alternatively, spread liberally with a spatula. Top with decorations, as desired.
Un-iced cupcakes suitable to freeze. Not suitable to microwave.Note