Abandon that and do this......
http://www.bbc.co.uk/food/recipes/velvet_chocolate_torte_42806THE most lovely choccy mousse cake ever.....by Queen Mary Berry
You can even watch the Food and Drink Xmas programme on I player to watch her do it....Divine!
I made a big one, froze it, semi thawed and used a cutter to make a few small individuals. Saved the rest in the freezer for later, topped the little ones with raspberries and shaved chocolate.
Guests went bonkers for them!