I've made chocolate cage cakes before, but never brilliantly. In fairness, this isn't brilliant but it did get a lot of attention. The whole process is very, very simple and is very handy for covering up the less than brilliant buttercream smoothing I do on the sides. Did I mention I hate buttercream? Gets sugar everywhere, dries hard and is far, far too sweet. I did try a cooked flour frosting the week before but my friend complained it wasn't sweet enough. Anyway, let's talk chocolate cage. You have a cake which you've covered with some kind of frosting. Assuming your oven doesn't suck as badly as my current one which messed up even the simple victoria sponge inside this cake, you'll have a cake. By itself, that's fine. To the cage - measure around the cake - and do it AFTER you've frosted it. I did this based on the cake pan and ended up about an inch short. (FYI not an issue, just squiggle some chocolate on a spare bit and patch...