Hi Sandy! Might want to use a spring form pan, put a layer of the cake in the bottom of the pan than fill it with softened icecream. Put it back into the freezer till that icecream gets really firm. Than take it out to ice it. If your doing alot of decorating it may be alot of in and out of the freezer. I don’t really recommend ganache or buttercream cause they will get pretty hard when frozen. I normally use a sweetened whipped cream like pastry pride your you can make a homemade version. Hope that helps!
Here is a link to an ice cream cake and directions from mycakeschool.com for their blog. It isn’t a traditional decorated ice cream cake but it may give you some ideas on the layering of the ice cream. Hope this helps. :D
I like the Ateco pans with the drop out bottom. I let the ice cream get soft but not melted…Smooth the ice cream out in the pan with an angled spatula or large spoon…then add a layer of cake…(if you don’t want any “real” cake in it, you can skip that part…but it’s alot easier with a layer of real cake..).. freeze for at least 24 hours. To take it out of the pan, get your board ready to put it on and run our cake pan until hot water until it’s loose and ready to slide out, quickly put on cake board. I would use gloves when doing this because it might get messy. Then stick it back in the freezer for a few hours before you decorate. (You can even do a couple layers of ice cream and cake and even put fudge, caramel, peanut butter, etc. in between.) Definitely make sure it’s super hardened before you frost.
“Riches Whipped Bettercreme” works good to frost with. If you use Ganache, you need to have it at a certain temperature so it sets up right and you can pour it on…but it’s a little tricky. I’ve never used buttercream but I assume it wouldn’t work very well. :)