i'm making a buttercream birthday cake and want to know if I could use a layer of chocolate ganache underneath the buttercream. I was planning on covering the cake with choc ganache, and putting it in the fridge to harden. then using a crusting buttercream over that to finish. will this work, will the buttercream still crust with a layer of ganache underneath, should i let it come to room temperature before i add the BC layer or will that make it mushy??

I've never heard of putting a layer of ganache under buttercream. Most of the time, it's either ganache with fondant on top or a buttercream finish.

How about butter cream frosting, then pour the ganache over that. here a picture of what it woul look like- http://cakecentral.com/gallery/2074619

I've never heard of that either. Is there a specific reason for wanting it that way?

Well I need it finished in buttercream as I need to decorate it so dont want a ganache finish. I thought having a ganache layer would give me a yummy and smooth base to get a really smooth buttercream finish. I usually finish in fondant so not used to getting super smooth buttercream finish and thought the ganache would help? kind of like crumb-coating with ganache so nobody's done this before...hmmm....

I have done this on 3 cakes I did for a family not wanting fondant. The ganache gives you a great undercoat to get a better looking frosted cake, and was very useful to me since I am better at fondant than BC. I ganached and then chilled the cake briefly before applying BC. Works like a charm!

thanks Dayti - I was thinking along those lines, that it would make getting a smooth buttercream finish easier! i'll find out tomorrow I suppose