It's easier to make buttercream with a standing electric mixer, but it can be done with a handheld one.
Cooks' notes:
·Buttercream can be made 1 week ahead and chilled, covered, or 1 month ahead and frozen. Bring to room temperature (do not use a microwave) and beat with an electric mixer before using.
·If egg safety is a problem in your area, you may want to use either pasteurized egg whites in the carton or reconstituted powdered egg whites.