There are several different styles of buttercream out there, including basic American buttercream and slightly more labor-intensive Italian and Swiss buttercreams. All are delicious ways to frost a cake or top a batch of cupcakes. I usually recommend that people make more buttercream than they need when they are planning to decorate a cake or cupcakes, since running out of frosting part-way through a project can be a real hassle, but making extra frosting means that you are going to have some leftover. What can you do with leftover buttercream, and can leftover buttercream be stored?
Leftover buttercream can be transferred to an airtight container and stored in the refrigerator or freezer until you are ready to use it. It can be kept in the refrigerator for about a week and frozen for several months. Leftover buttercream can be used just like a fresh batch of buttercream, once it is warmed up and ready to spread. All buttercreams should be brought to room temperature and rewhipped before you try to use them again, just to make sure that they are light and fluffy. If your buttercream is not completely thawed, you will find that it starts to look grainy and broken as you rewhip it. If this happens, just let it sit out a little bit longer and try again. Adding in an extra tablespoon or two of confectioners’ sugar can also help to thicken a defrosted buttercream slightly, if necessary.
Although it may be tempting to do so, I don’t recommend storing buttercream in your pastry bag. All types of buttercream will be best after they have been re-whipped to smooth out any lumps, so even though you are saving time by popping that pastry bag into the fridge, you’re going to have to cut it out end put it into a fresh bag for your next use anyway. If you only have a small amount of leftover buttercream – enough for just one or two cupcake – you probably won’t want to save it because it could take a while to find an application for such a small amount, and you will probably end up having to make a new batch the next time you bake something anyway.