Sift the powdered sugar

Sifting the powdered sugar before using it is another technique to ensure that your buttercream comes out lump-free. One of the worst baking mistakes you may make is forgetting to sift some ingredients. Sifting makes flour, sugar, and other dry materials airier and lighter by removing all the undesirable clumps. What then, if you don't have a sifter? If you don't have a sieve, don't worry; you can still learn how to sift ingredients.

As with flour, you may simply whisk the confectioners' sugar into a finer consistency by breaking up the sugar clusters that have formed. It won't always be as light as a sieve would make it, but this simple exercise will surely be beneficial. Sifting can seem like a pain, but once you realize how much of a difference it really makes to your frosting, you'll be glad you took the time to do it.