Hi all! I'm new to the forum, although I've been studying various threads on here intently for months.. and I'm also fairly new to cake decorating in general! I'm currently working on an engagement cake which is due next weekend. It's for 150 people, I'm making a 3 tiered cake consisting on 12", 10" and 8" rounds with two 3" layers per tier (maybe a little less by the time I level them) for extra servings. I went will all mudcakes; the bottom is dark chocolate, middle is caramel and the top is white. After a few disasters the last of my 6 cakes is finally in the oven. Phew! Not that any of that has anything to do with my query.. but I've decided to go with ganache frosting with the mud cakes because they go so well together. I've read in a lot of instances that people prefer to work with ganache under fondant. I've only ever used buttercream or a buttercream ganache.. I think I'm leaning more towards the buttercream ganache.. for cost more than anything because god only knows how much I've spent on chocolate already..! But I'm wondering if you can use any ganache recipe for 50/50 with buttercream? Sorry for the babble.. should learn to cut to the chase! :)

I'm sorry, but I did not understand if you are planning to use fondant, or if you wanted to know if ganache could be used alone?  Ganache can certainly be use alone and does not need to be covered in fondant.  If you are planning to use fondant, you can use ganache, buttercream, or buttercream ganache underneath.  The advantage of ganache (2:1 choc to cream for dark, 3:1 choc to cream for milk or white)  is that it is firmer, holds shapes and corners better, and some folks find it is a better, sturdier foundation for fondant.It also may be the better choice if the venue will be warm.   Many awesome bakers use buttercream under fondant.  So you can do whatever you like!  Best recommendation:  make some small sample cakes to play with, and if unsure, go with a stiffer foundation, rather than a softer one - more forgiving.  

I just realized this didn't answer your opening question!  my favorite buttercream is Toba Garrett's Chocolate Buttercream which is basically half buttercream and half ganache. It is a lot of work, but it is delicious and dark brown in color.  More often, I just mix ganache with SMBC  to the right taste and color and it also wonderful (even better with a little Godiva chocolate liqueur) but will be a lighter brown color. I have never mixed ganache and ABC (I rarely use it) but I can't imagine it wouldn't work. Trial and error!

http://www.epicurious.com/recipes/food/views/Chocolate-Buttercream-109248