Preheat the oven to 180ºc/gas 4. Line 2 set of yorkshire/muffin tins with cup cases and set aside.
With an electric whisk, beat together the margarine and sugar until pale and fluffy.
In a separate bowl, add the vanilla essence to the egg and in another bowl add the baking powder to the flour.
Add third of the egg to the margarine mixture and beat together with a wooden spoon, then add a third of the flour and combine, then repeat until all the cake ingredients are mixed together.
Divide the mixture between the cake cases and place in the oven for 25mins, until they spring back up when lightly pressed in the middle.
When baked, remove from the oven, remove the cakes from the tin and place on a cooling rack.
To make the buttercream, beat the butter until smooth, gradually add the sifted icing sugar until all combined, add the milk and vanilla extract.
If using food colouring, divide the buttercream into other bowls, add the colouring and mix together. Using a piping bag and nozzle, decorate your cakes and sprinkle additional cake toppings. Transfer to an airtight.
