Sock monkey, the ratio of cream to chocolate changes depending on what you're using it for. For truffles where I want it soft I use almost 50/50 cream to choc. For cakes though, especially if you want it to set and hold the choc pieces on, you want it a bit firmer, so if I was using 500g choc (dark or dark/milk mix), I'd use approx 200g double cream, 25g glucose and 25g. butter. I don't fret if I weigh a bit more or less, it's reasonably forgiving. If you use white choc you need less cream.
Ganache will definitely hold those pieces. You will just need to cover the cake, let it at a bit, then add your choc designs by piping a blob of ganache into each bit and placing it on. No trouble
If you're really worried about stacking, why not head to Tesco and buy a couple of their £3 cakes to use? It'll be a good deal cheaper in time and money than you making them, and even if they're the same size you can still practice dowling and stacking. Like doing a tiered cake in miniature
So, it's the pouring type of ganache that's 500g chocolate (maybe 250g choc/250g Nutella), 200g cream, 25g glucose & 25g butter? I seriously confused myself by researching ganache in the early hours of the morning. I had always assumed ganache was the pouring type that usually sets quite shiny until I watched some video where it was saying you can wait for it to firm up a bit then apply it or leave it for a while, then whisk for a fluffier texture. Also some people were boiling the cream then adding it to the chocolate, others were just melting everything together in a pan. I think I need to put myself on a Google ban and just start baking! I expect I'm driving you all mad as well as myself.
That's a great idea about using cheap supermarket cakes to test the stacking. I was planning to do 10", 8" and 6" cakes, as that works out roughly enough to serve 75, so I could make the 10" and buy smaller ones. I guess seeing how well the bottom one copes is the most important bit.
I actually have a sock monkey, so I hope he's not sick!! Maybe it's some kind of sign of how this cake is going to taste, hehe.
Edited by Sock Monkey - Today at 4:54 am