Does anyone know where I can get a tutorial on how to do this cake? I have been asked for a qoutation, but I don't know how to make it and if I will be able to do it.
That looks like two tall tiers (each one with at least 6" or 15cm height).
A tutorial on "how to wrap cake with chocolate" is posted somewhere on Cake Central--use google to find it fast.
I can tell you to mix the dark chocolate and white chocolate for the middle colour--DO NOT use milk chocolate because it causes trouble. Also don't be afraid because this is an informal ruffly look, some mistakes are OK.