Frosting a cake with perfectly smooth sides and a crisp top edge is not a skill reserved for just professionals. Using a few tools and simple tricks, anyone can make a beautifully frosted cake.
To create a level, stable cake, you must start from the bottom. Not only do you need a delicious, well-structured cake, but the cake layers should also be equal in shape and size. Most cakes are not 100 percent ready to go straight from the cake pan. You will need to “torte” the cakes, or cut them so the layers are flat and the correct height.
Begin by chilling the cake layers
Before cutting or frosting a cake, be sure the cake layers are completely cool. After they are removed from their pans, it is best to wrap the cakes in plastic wrap and chill them in the refrigerator for a couple of hours. A chilled cake means fewer crumbs when it is cut or handled.
Flatten the top of the cakes
Next, any domes created during baking must be removed. Start by placing the cake on a clean turntable or cake board. Use a long serrated knife held parallel to your work surface to score the top of the cake where the dome starts. As you spin the turntable, begin cutting into and across the cake. Keep the knife as level and parallel to your work surface as possible and cut in toward the center of the cake until the dome detaches from the body of the cake. If the cakes do not have domes on top, use the same technique to make sure all the layers are the same height.
Score and cut the cake into layers
Many recipes call for the cakes to be split into multiple layers. For two even layers, measure the height of the cake, and divide that amount in half. Score the cake halfway up with a serrated knife or mark with toothpicks. While spinning the turntable, carefully cut the cake in half horizontally with a long serrated knife. For even layers, keep the knife as level as possible and only cut a little a time.
Before assembling a cake, decide how you will layer it. When there are multiple layers to choose from, select the most stable one for the bottom layer. Sometimes cakes break and crumble a bit, but you will want to use the sturdiest layer as the base of your cake. Use the imperfect layer(s), if any, as the middle and save the second-best layer for the very top. If possible, the top layer should be placed cut-side down for minimal crumbs when frosting.
Fill the cake
The most beautifully frosted cakes start from the inside out. Depending on the cake recipe and filling(s) involved, filling a cake may be a bit tricky. For cakes with softer fillings, follow these guidelines.
Place a cake board in the center of the turntable and place the bottom cake layer on top. Prepare a pastry bag with a round piping tip and fill it one-half to three-quarters full with buttercream or your frosting of choice. Pipe a ring of buttercream 1/2 to 3/4 inch (12 mm to 2 cm) high around the top edge of the cake layer. Fill the ring or “frosting dam” with the filling of your choice. Even out the filling with a small offset spatula, if necessary. Top with the next layer of cake and repeat. Once all the layers are filled and stacked, make sure that the cake is sitting up straight and is as level as possible. If the cake is leaning at all, use clean hands to push and manipulate the cake layers slightly so that everything is even.
Apply the crumb coat
The first coat of frosting is called the crumb coat. This thin layer helps hold in all the crumbs and prevents bits of cake from getting into the final coat. Start by placing a medium dollop of frosting on top of the cake. Using an offset spatula, begin to spread it out. Continue coating by applying frosting to the sides of the cake. The crumb coat should be even and completely cover the cake, but does not need to be perfectly smooth. Refrigerate the cake uncovered for 10 to 15 minutes to set it before adding the final coat.
Cover with an even layer of frosting
Swiss Meringue Buttercream makes for the smoothest finish, but the same techniques should be used with whatever frosting you choose. Even cakes with a rustic finish should start with this process.
Starting with the top of the cake, place a generous amount of frosting on top of the crumb coat. Use an offset spatula to begin spreading out and flattening the mound of frosting on top. Spin the turntable simultaneously to create an even layer of icing. Push any excess frosting to the edges so that it creates an overhang off the top edge of the cake. The frosting here does not have to be perfect, as we will be smoothing out the top again later on.
Using an offset or straight metal spatula, attach the frosting that may be overhanging from the top of the cake to the sides of the cake. Working on only the top half of the cake, begin applying frosting to the sides of the cake. The frosting does not need to be smooth, but should be applied in an even layer. Continue on to the bottom half of the cake.
Once there is an even layer of frosting on all sides of the cake, begin smoothing the frosting out. While spinning the turntable, use an offset spatula to smooth out the final layer, removing any excess frosting and adding more, when necessary.
Smooth out the cake
After this first round of smoothing, it’s time to put our tools to work. Place the icing smoother parallel to the side of the cake. The long, smooth edge should be touching the cake and the bottom edge should sit directly on top of the turntable or cake board. Keeping the icing smoother still, slowly begin to spin the turntable. The icing smoother should pick up any excess frosting to create a smooth finish. After a couple of spins, stop and step back. Fill in any gaps with frosting using a small offset spatula and check to make sure the sides of the cake are straight. Continue to use the icing smoother until you are satisfied.
As the sides of the cake are smoothed out, frosting will be pushed up toward the top of the cake. To remove this lip of frosting and to smooth out the top, carefully take the edge of an offset spatula to pull the lip of frosting toward the center of the cake. Keep the spatula as level as possible and try not to interfere with the frosting on the sides of the cake. Continue around the entire top edge. Finally, lightly place the edge of the icing smoother on the top of the cake. Give the turntable one final spin to even out the top.
Tips and troubleshooting for frosting a cake
- When crumb-coating the cake, do not return any frosting that contains crumbs to the original bowl of clean frosting.
- Always clean off the spatula and icing smoother between frosting applications.
- When working with an offset spatula, focus on using the center of the spatula as opposed to the tip of the spatula for more control.
- Work with a small amount of icing at a time for better control and cleanliness, especially when just learning how to frost a cake.
- Use the turntable to your advantage. Let the spinning action work for you when leveling out the top and smoothing out the sides.
- If you do not have a turntable, try placing the cake and cake board on top of an inverted mixing bowl and carefully rotate the cake board as you go.
- Apply a thick enough layer of frosting to the sides of the cake so the cake layers do not show through.
Essentially, you will be applying more frosting than needed in the end, since some of it will be removed when smoothing.
- If the cake or frosting ever seems soft or runny, chill the cake in the refrigerator for 15 to 20 minutes.
- If the buttercream appears to have air bubbles or is too thick, try remixing the frosting until silky smooth.
- For an even smoother finish, heat a metal spatula or icing smoother by running it under hot water. Dry and continue the smoothing process. The warmed metal will help by slightly melting the frosting. Try this technique on a chilled cake.
- You will need about 3 cups (720 ml) of buttercream to frost a three-layer 6-inch (15-cm) round cake. You will need about 4 1/2 cups (1 L) buttercream to frost a three-layer 8-inch (20-cm) round cake.