This buttercream can be prepared in advanced to be used later. Simply store it in an air tight container in the fridge or pop in a ziplock bag/air tight container and freeze. When ready to use, bring buttercream to room temperature and then beat with a stand/hand held mixer until it is light and fluffy. Chilled/frozen buttercream can be softened in the microwave in 20 secend increments. It will last in the fridge for several weeks and up to 3-4 months in the freezer.