How to Frost a Smooth-Sided Cake (Even with Sprinkles in the Frosting)
Think of baking a layer cake like a construction job. The cake layers are the wood, the foundation of the project; the icing is the spackle, the glue that holds everything together. Icing a cake is much more than just adding a pretty decoration. In addition to providing a smooth, clean finish, icing also ensures that your layer cake remains sturdy and structurally sound. Sure, you can get fancy with flowers and ruffles, but this technique for how to frost a smooth-sided cake provides a basic foundation for constructing a great layer cake. It'll be one that you turn to again and again for celebrations big and small.
It all starts with the crumb coat, a thin layer of frosting spread evenly over the cake. This layer of frosting is intended to seal all the crumbs in (hence, the name). The crumb coat is essential to achieving a smooth finish on your final coat of frosting. Chilling the cake after the crumb coat allows time for the frosting to set—otherwise, you risk the frosting melting and sliding down the sides of the cake.
From there, follow our instructions for frosting a cake with perfectly smooth sides. After achieving this simple structure, you can add all the bells and whistles you'd like (think flowers, sprinkles, and other decorative elements). Looking for more inspiration? Our Confetti Cake with Vanilla-Sour Cream Frosting is a great place to start. Here's our step-by-step guide to decorating a smooth cake, even with sprinkles.
Put a cake plate on a stand. Place one cake layer on plate, and spread plain frosting on top. Repeat with two other cake layers. Use a bench scraper or large offset spatula to spread a thin layer of plain frosting (about ½ cup) on sides of cake, rotating the stand as you work. Chill 30 minutes.
Using an offset spatula, spread a thick layer (one cup) of frosting with sprinkles already incorporated on the sides, rotating the cake as you work to make the sides as smooth as possible. Wipe off excess frosting from the spatula as you go. Fix cracks by spreading a little more sprinkle frosting. Smooth the sides with the spatula, if needed.
To make the top edge of the cake look smooth and straight, spread excess icing toward the center. Then smooth the top with the spatula.