Cooks' note:
• Buttercream can be made 1 week ahead and chilled, covered, or frozen 1 month. Bring to room temperature (do not use a microwave) and beat with electric mixer before using.
• Buttercream can be made 1 week ahead and chilled, covered, or frozen 1 month. Bring to room temperature (do not use a microwave) and beat with electric mixer before using.