Hi Madeleine! You can make buttercream ahead of time but it'll need to be put back into the mixer with the paddle attachment and mixed until it warms up and the emulsion comes back together. Oftentimes buttercream breaks during this process, but don't worry and just keep mixing, it'll smooth out. Applying a bit of heat can make this easier, it seems like an odd kitchen tool but warming the bottom of the mixing bowl with a hair dryer can help to reconstitute the mixture. We hope this can help and happy baking! 

• Reply