I hear of people whipping ganache before using it as a filling for cakes. The last time I tried to whip mine, it separated, but I whipped it before it was fully cooled. Who has done what? Would love any opinions/suggestions you guys have!

I've whipped my ganache and I couldn't tell any difference before and after, so now I just save myself the trouble and put it on without whipping it. It doesn't fluff up or anything like egg whites or whipped cream would. It doesn't get any lighter in color. It has no appreciable difference in texture. Who needs an extra step in baking and decorating when there are so many already? IMHO.

^ sounds like your ganache didn't whip then Marianna. Whipped ganache does get lighter & airier if you whip it properly.

I prefer unwhipped myself...you kind of loose some of the great 'fudgeyness' by whipping it IMO.

I whip mine after it sets and cools overnight. I just leave it on the counter in a bowl covered with plastic wrapped touching the chocolate to keep a skin from forming. When I whip it, it does thicken and lighten in color. Basically, if you whip it correctly, it is the chocolate you would find in the middle of a truffle. Don't forget there are different ratios of heavy whipping cream to chocolate depending on the type of chocolate you use.

I use the whipped ganache as a crumb coat underneath my fondant. It is amazingly easy to smooth.