Rainbow skittle cake

Grease a 19cm x 30cm lamington pan. Line the base and sides with baking paper, extending the paper 2cm above pan edges.

Prepare the cake mix according to the packet directions. Divide among three bowls, tinting each with a different food colouring. Alternately place spoonfuls of each mixture into the prepared pan. Use a skewer to swirl through to create a marbled effect.

Cook in a moderately slow oven (160°C) for about 25 minutes, or until cooked when tested. Remove from oven and stand in the pan for 10 minutes. Turn out onto a wire rack to cool.

To make frosting, combine all ingredients in a bowl and stir until smooth.

Spread frosting over cake. Decorate with Skittles.