This cake was made for a friend from work who is moving on to greener pastures. Take the recipe Basic Cake Mix and double it. Make it all in one bowl with added orange zest up until you are ready to add the flour.
Split the mix in two and add 200g of flour to the one mix (the plain) and 175g flour and 25g cocoa powder to the other. Fill two piping bags with the respective mixtures and pipe into 3 greased cake tins in circles, one inside the next etc until the mixture is used.
Put in the oven at 160-180c for around 20 minutes. Make up the butter icing with a good dollop of stork or butter and cream until soft. Add the juice of half an orange and cocoa powder in the icing sugar until stiff.
Once the cakes have cooled, sparingly use the buttercream to construct the three sponges together. Next cover the entire cake in the buttercream until smooth and then decorate with your choice of decorations -I used orange coloured choc buttons and chocolate orange segments.
When you slice into it it will have a beautiful marbly stripy effect of sponge and a wonderful flavour!