After reading about using ganache under fondant for an icing, I am gonna give white chocolate another try for my mom's lemon bday cake today. However, I need to get it melting asap so I can cool it down to spreadable consistency.

How much do I need for a 2 layer 9 inch round cake? I think it is a 3-1 ratio so correct me if I am wrong.
I am using Callebaut white chocolate discs, so how many cups of that (unmelted) would you use to how much cream? Or do I have to melt it down to measure...I want to make it as easy as possible.

If you're not going to fill with it, I would use 12 oz cream to 36 oz. white chocolate. That would give you enough to cover without being scrimpy or stingy.

so can I weigh out the 36 oz. of chocolate, or do I melt and use liquid measure? Or can I just measure out dry chips...The white chocolate I'm using is in regular size chips not discs if that helps.

Weigh out the chips. Mine come in 12 oz. bags, so I use three bags.

Measure the cream in a liquid measure cup ( 12 oz = 1.5 cups).

Thanks a lot, mine came in a 5 lb. bag so it's a good thing I have a scale! (That will yield the same measurements, right?)

so I weighed out the chips, and 36 oz. came it about to be about 6 cups...does that sound right? It looks like a lot.

My 36 oz comes closer to 4.5 or 5 cups, but weight is what you go by. I'm sure you're using a different product than I am.