Buttercream will last in a tightly covered container in the fridge for 2 months. Let the buttercream come to room temp for at least 30 minutes before using if it has been stored in the fridge. Mix well until it is smooth again and use to decorate cookies or cookie cakes. If wanting to color your buttercream, I highly recommend using gel food coloring for vibrant colors. Liquid food colors are not as pigmented and can water down the buttercream.
Keyword American buttercream, butter, buttercream, Cookie cake