The icing that I had to use when I took my cake decorating class was made of shortening and powdered sugar. Even though it was easy to learn on, and it's what many bakeries use, I simply couldn't bear to have it in my mouth.
Fear no more! Rose Levy Beranbaum's Neoclassic Buttercream is pure butter and fabulous! I was scared to make it (add boiling scary-hot sugar syrup to egg yolks, beat like crazy, add lots & lots of butter, continue beating like crazy), but now that I've tried, there's no going back. It's light and smooth, super delicious. Since today was just practice icing on practice cupcakes, I left everything very plain. I can hardly wait to use different flavors.
Her recipe for Mousseline Buttercream is stiffer, supposedly more appropriate for piping decorations. So I will try that next.