Three Colour Mini Cakes

For the cupcakes: heat the oven to 180°C (160° fan) 350°F gas 4. Place paper cases in a 12 hole bun tin.

Mix together the butter, egg, yoghurt, lime juice and zest.

Stir together the flour, baking powder and sugar in a mixing bowl. Add the egg mixture and stir until blended.

Spoon the mixture into the paper cases and bake for 20-25 minutes until golden and springy to the touch. Cool in the tin for 5 minutes, then place on a wire rack to cool completely.

For the buttercream: beat the butter in a bowl until soft. sift in half the icing sugar and beat until smooth. Add the remaining icing sugar and 1 tablespoon milk and beat the mixture until creamy and smooth. Beat in more milk if necessary, to loosen the mixture.

Divide the mixture evenly between 3 bowls. Add a few drops of green food colouring to one bowl; orange food colouring to another and the yellow food colouring to the third bowl.

Spread the buttercream over the cakes.

For the frosting: sift the icing sugar into a bowl and beat in just enough egg white (you won't need all of it) to make a smooth frosting that is thick enough to pipe. Put the frosting into a piping bag and pipe lines and dots on top of the buttercream.