Hi. I had such a miserable experience trying to cover a ganached (chocolate, not white) cake with fondant this weekend, I'd love to know where I went wrong for next time.
I followed the tutorial by Inspired by Michelle. I loved how easy it was to smooth the ganache. when i covered with fondant (satin ice) i ended up with a air bubbly, elephant skinned mess. I've never had this issue when covering with buttercream. I let the ganached cake sit at air temp overnight, brushed the cake evenly with hot water, rolled out my fondant, and covered quickly. SO many bubbles! and the elephant skin all over! after this experience, i'd never want to use ganache again, but so many swear by it, maybe i'll try again if i can get tips on what went wrong!
AI suspect the problem was that you didn't knead the SatinIce nearly enough. You have to warm it up enough yo activate the gums. Its nearly impossible to over-knead it, but entirely likely to under-knead it.
Def not a expert but I think the hot water could have been the problem. I have only ever used room temp water otherwise you are creating a warm area under your fondant which could result in bubbles as it cools.
You are right in using hot (boiling hot) water. However, you should apply the water BEFORE kneading and rolling out your fondant. This gives the water some time to evaporate slightly, making the ganache tacky, rather than wet. Before applying the fondant, just check again to ensure the entire cake is still tacky with no bare areas which will lead to bubbles.
Your problems are more likely to have been the fondant used, than the ganache itself. Follow Leah's advice on kneading and try again on your next cake.