I am doing a carved cake that has a fair amount of small details/indentations. What's the best thing to use under the fondant that will hold some shape when I push and shape the small lines/etc.?

I was thinking of trying white chocolate ganache, as I've seen some good things said of it under fondant here. I know I need to keep the ratio at 3:1 to get the WCG to set up firmer, but I've honestly never worked with it. I am doing a test cake in the next few days, so I guess there's no time like the present!

My husband just ran out to get my ingredients (White Chocolate Rum Whipped, from CC).

Any thoughts on other options that would give me the support and firmness I need under my fondant?

Oh, on using BC, I've traditionally used BC under my fondant, but when I push on it to make designs/indentations, the BC seems to go where it wants to after a while!