Hi there!  i will be making my first ever fondant covered cake and i would like some ideas/recipes for fillings i could use.  It will be a single tier, 3 layer cake.  I am making chocolate WASC cake and yellow WASC cake, one layer of each, and a marble layer.  I will be covering the cake in chocolate ganache before covering in fondant and was thinking about using whipped ganache as the filling.  But i am thinking it might be too heavy and sweet.  Any ideas for fillings that would lighten up the cake and go good with the flavours would be helpful.  Also, i will be making the cake on Wednesday and serving in on Friday, don't know if that matters.  Thanks in advance!!

I think ganache might be too heavy as a filling if you're also using it to ice the cake.  For chocolate, I almost always do either an Oreo filling or a peanut butter cup filling.  I just crush Oreo cookies into my buttercream.  I actually use WAY more Oreos than buttercream.  It's super good that way.  For the peanut butter cup filling, I whip 1 cup of peanut butter with 1 stick of butter (1/2 cup).  Then I add some warm whipping cream and beat that in, then add sifted icing sugar to taste.  Then I crumble up Reese's cups and add those in.  You could use the Oreo filling for either the chocolate or marble cake.  For the yellow, I would be inclined to just fill it with a regular vanilla buttercream.  It would be a nice contrast to the ganache on the outside.

I think a whipped ganache makes a good filling, it isn't too heavy at all but that's just my taste. You might do white and chocolate ganache.