In two separate bowls, mix the two mousse according to the direction of the package. For the sponge, see my recipe for the Victoria Sponge. Then after cooling off the sponge, cut it across into 3 sections.

Assemble the ingredients as follows: sponge, white chocolate mousse, sponge, dark chocolate mousse, sponge and finish off with white chocolate mousse. Sprinkle top with cocoa powder to decorate.