Creamy, silky and smooth Swiss Meringue Buttercream is the perfect frosting for cupcakes, layered cakes and other baked goods. Not overly sweet, light, stable at room temperature and absolutely delicious!
Wipe clean the mixing bowl with a clean towel or with paper towels to remove any grease or oils. Grease prevents the meringue from setting.
Use a double boiler or set one up by placing a mixing bowl over a pot filled with about 1 - 2 inches of simmering water at medium-low heat.
Place the egg whites and sugar in a heatproof mixing bowl (for convenience, use your stand mixer bowl). Make sure the bottom of the bowl doesn’t touch the simmering water.
Whisk the egg whites occasionally while it warms up. When the mixture has warmed, whisk it constantly until the sugar is completely dissolved and no longer grainy to the touch about 3-4 minutes. You can also check the internal temperature with an instant read thermometer. The mixture should reach an internal temperature of 160 degrees Fahrenheit.
Transfer the mixture to the bowl of a stand mixer (unless you are already using it) fitted with the whisk attachment or use a handheld mixer. Beat the mixture over medium-high speed until stiff glossy peaks form and the mixture is no longer warm, about 10 minutes.
Switch the stand mixer to the paddle attachment. With the mixer on medium high speed, add the cubed butter one piece at a time and mix until the butter is fully incorporated before you add more butter.
Next, add the vanilla and salt and beat for about 40 seconds. The buttercream should be thick and creamy.
Notes
Use fresh egg whites not carton egg whites.
Wipe the mixing bowl clean before you whip the egg whites.
Make sure your egg whites don't have any yolks.
If your meringue looks curdled or separated after adding the butter, simply keep beating it. The mixture will reincorporate and become smooth again.