Nigella Lawson has a recipe for a chocolate cake that doesnt turn into a disaster if it falls apart. Its her celebration cake. Have not got it to hand, but the icing is what sticks it together. One 100mg bar of darkest chocolate. Heat some cream, not to boiling, double I think, and drop into it the chocolate, chopped into finest bits. Then electric whizz with whisk till you have a thick glutonous chocolate creamy mess. Pour this over the cake, perhaps pushing cake into right shape and filling cracks, it should stick it together. good luck!