First buy your cocoa beans,,,,,,,If you are genuinely interested and not just asking out of idle curiosity, I suggest you write to Cadbury's in Bournville. They obviously are not going to give you any trade secrets - it is quite a complicated business anyway-but they would probably send you info on the general process and if you have the opportunity, depending on where you live, you could visit Cadbury World, sited next to the factory.