Preheat the oven to 190°C (170°C Fan, Gas Mark 5). Line a cupcake tin with 10 Baking Cases. In a mixing bowl, beat the margarine with the sugar until pale and creamy in texture.
Gradually whisk in the eggs then sift the flour and Baking Powder on top. Using a large metal spoon, fold in the dry ingredients.
Spoon the mixture into the Baking Cases and bake in the oven for 16-18 minutes until risen, lightly golden and just firm to the touch. Transfer to a wire rack to cool.
To decorate, put the white fat and butter in a bowl and beat until smooth, glossy and pale. Gradually, sift and beat in the icing sugar until creamy and soft then add the Madagascan Vanilla Extract. Divide the butter icing into equal portions based on the number of different coloured icings you want to make.
Add a different Gel Food Colour to each portion, and mix thoroughly to make different coloured icing, using the guide below:
Red 20 drops per 25g icing
Blue 10 drops per 25g icing
Yellow 20 drops per 25g icing
Green 30 drops per 25g icing
Orange 50 drops per 25g icing
Pink 20 drops per 25g icing
Violet 30 drops 25g icing
Black 1 tube 25g icing
Fit a large piping bag with a 1cm (½ inch) large closed star nozzle. Spoon one colour icing into another piping bag and another coloured icing into a third piping bag. Cut 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.
Repeat the loading and piping with the other colours of icing in separate piping bags.