A Swiss buttercream is made with the same ingredients, but the sugar and whites are heated together over a water bath, until it's almost too hot to touch. At that point, it is whipped until cool, and the butter is added.
I have also seen this done with whole eggs, and just yolks. That obviously would yeild a richer and yellower buttercream.
Good luck, bakerbebe-- I hope you broaden your horizons

. It's actually less messy to work with than ganache.