Rich, creamy, and satiny smooth, this Swiss meringue buttercream is perfect for decorating all types of cakes and cupcakes.
Using an electric mixer fitted with the whisk attachment, whisk egg white mixture until stiff peaks form and meringue is thick, glossy, and room temperature, about 10 minutes (start with low speed and gradually increase to medium-high). Make sure the bowl isn’t warm before adding the butter, otherwise it will melt.
On low speed, add a few tablespoons of butter at a time, beating well after each addition until incorporated. Once all butter has been added, keep beating until very smooth. If at some point the mixture curdles, keep beating until smooth again. Add vanilla and beat on low speed until combined. At this point, you can add any additional flavor (such as extracts), then beat until smooth.
Having issues with your buttercream? Check out the Troubleshooting section of my white chocolate Swiss meringue buttercream post to learn how to fix any problems that arise.