"This is the very lightest chocolate cake of all, the reason being that no flour is used – it's simply made with eggs and cocoa powder. It's very fragile, almost soufflé-like, but once you've tried it you'll never want any other kind. Don't forget to start this a couple of days ahead if possible by heating the prunes with the Armagnac and leaving them to soak up all the delicious flavour...."