“Green colour is chlorophyll in Hoppers’ colouring, black is activated charcoal, brown is carob. Fondant is a marshmallow fondant made in the Thermomix with salted buttercream underneath. The cake itself is a double layered vanilla magic bean cake.
For the squares, I rolled out the coloured fondant on baking parchment with a bunch of cornflour to stop it sticking and then just sliced it into rows and squares with a pizza cutter.”
Instructions for how to make Marshmallow Fondant both in a Thermomix or on the stove-top can be found at Domestic Diva’s blog.
Recipe for Magic Bean chocolate cake is here; just substitute kidney beans with cannelini or butter beans and the carob with rice flour and add equiv 1 vanilla bean.
I suspect the cake was greener than this picture suggests.