Yes. absolutely. If you'd like to freeze the whole cake, freeze the 2 layers separately. Wrap well in several layers of plastic wrap and/or foil for up to 6 months. I'd make the ganache fresh when you want to serve the cake. If you're freezing leftovers, simply store in airtight plastic or glass containers for up to 6 months. Around 2 hours should be enough time for it to defrost or let it defrost slowly in the fridge overnight.