How to Store Buttercream
If you have leftover buttercream frosting, you can store it in your fridge for a couple of weeks. Just put your buttercream frosting in a covered container with a lid. When you're ready to use it again, just take the frosting out of the fridge and let it get to room temperature again. Using a hand-held mixer, just mix the frosting again until you have fluffy buttercream frosting again.