See, I think this is a big mistake - I have spent many a time struggling to get this thick paste onto the cake when the air bubbles are pushed out when pressured and covered with sugarpaste. Then fighting to get a smooth finish with a hot knife - why do so many recipes and professionals tell you to do this?
I'm not convinced that aerating for the filling either if the weight of the cakes pushes the air out - unless you when piping a huge thickness between layers. I have looked at the layers after being cut and I cant see many air bubbles - the ganche is just a chocolate paste.
Can someone explain to me the relevance of this or whether it is a pointless exercise when using it as a base of sugarpaste.
I don't whip my ganache. I just use it straight out of the container. Any manipulation will make it start to set, from just simply stirring it to the motion of putting it on the cake. There's no reason to whip it, unless you are looking for a little lighter texture for a filling. But, if it sets too fast, you would have to heat it a few seconds and soften it up. If I ever do whip it, I only use a paddle, not the whip attachment.
but oh, a whipped ganache is like heaven on the tongue. my nephew's birthday cake is filled and frosted with whipped and it is wonderful.