The ratio is not clear to me for the white chocolate ganache.

It's 3:1 for white chocolate, is that cups or weight?

Thanks

It's 3 to 1 by volume. I use the recipe in the Planet Cake book. Comes out great, especially since I got a small electronic kitchen scale so that I can do it by volume.

3:1 for White and milk
2:1 for dark

I use for example, 400g dark: 200ml cream. 600g White: 200ml cream etc...

so... using the example of 600 g white choc to 200 ml cream, how much ganache does that make?

Is it enough to torte and ice a 10' cake, or torte or ice only?

Measure by weight, not volume, for both the chocolate and the cream.

http://cakecentral.com/cake-decorating-ftopict-729560-.html&sid=2023a3f99b69922731ea83c84cdc313c

Here's another topic about ratios that may help you. EnglishCakeLady has posted a link to a ganache calculator which tells you how much ganache to make for each different sized cake. Click on the link and it will download an excel file to your computer.