What kind of buttercream do you use on your cakes? I've always used a butter/powdered sugar or hi ratio shortening/powerded sugar buttercream but I can't always get it as smooth as I'd like. I've tried the viva paper towel method but I guess I'm too much of a perfectionist. I've tried a swiss meringue that came out beautifully but is it durable enough to use under fondant? Can you pipe with it? My concern is that the swiss meringue would be too soft.

ASMBC is my go-to bc. It works great under fondant, although I prefer ganache under fondant. It's holds up much better. SMBC does well with piping. It can get soft if you are handling it too long...otherwise works like a charm.