Preheat the oven to 190°C (170°C Fan, Gas Mark 5). Line a cupcake tin with 9 Cupcake Cases. In a mixing bowl, beat the margarine with the sugar until pale, and creamy-light in texture.
Gradually whisk in the eggs and add a few drops of Natural Vanilla Extract, then sift the flour and Baking Powder on top. Using a large metal spoon, carefully fold the dry ingredients into the creamy mixture.
Spoon the mixture into the Cupcake Cases and bake on the middle shelf in the oven for 20-22 minutes until risen and just firm to the touch. Transfer to a wire rack to cool.
To decorate, put the butter in a bowl and beat until soft and pale in colour. Gradually sift and beat in the icing sugar until creamy and add 1 tsp of Natural Vanilla Extract. Divide the butter icing in half. Keeping one portion plain, further divide the other portion between 3 bowls and squeeze a small amount of a different coloured Gel Food Colour to each bowl and mix well until desired colour is achieved.
Fit a large piping bag with a 1cm large closed star nozzle. Spoon one third of the plain icing into another piping bag, and one of the batches of coloured icing into a third piping bag. Snip the ends off both bags to make a 1cm gap. Flatten the bags slightly and place them side by side in the bag with the nozzle. Squeeze the icings evenly down the bag towards the nozzle and twist closed.
Starting in the middle of a cake, pipe the icing round in an anti-clockwise direction to cover the top of the cake then continue piping round to form a swirl on top. You should have enough icing for 3 cakes.
Repeat the loading and piping with the other 2 batches of coloured and plain icing. Decorate the cakes with Wafer Butterflies just before serving.