I just want to share a resource with all of you who are making the foray into ganaching cakes. I have developed a excel spreadsheet (called "The Ganacherator") to assist with how much ganache to make to cover and fill your cake. I decided to develop this tool in answer to the question..."How much ganache do i need to cover a x" round/square cake?" and it has gone through a few versions. The most recent of which is the addition of measurements in oz. and fl. oz. for chocolate and cream. It also has grams and mls. for the metric amongst you. I think it is fairly self explanitory but please do not hesitate to come over to www.facebook.com/iwantsprinkles and ask any questions you like, or email me at the address on the spreadsheet.
The ratios rely on the use of pouring cream (at least 65% fat) or whipping cream (which is the same fat % but with vege gums to make it hold it's shape when whipped). I apologise if I am using foreign terms, that is just what we call them in Oz.
OMG, sorry for the essay. Anyway, if you got this far, here are the links. I periodically update the program and re-launch it from Facebook/iwantsprinkles. I'm also planning to add some functionality around recipe scaling etc. so I'll keep you posted. Okay, I'll shut up now.
http://dl.dropbox.com/u/28726919/The%20Ganacherator.xlsx (newer version of Excel)
http://dl.dropbox.com/u/28726919/Ganache%20calculator_97_2003.xls (older versions of excel)