Swiss Meringue Buttercream

Ingredients

Whisk egg whites, sugar, and corn syrup together in a microwave-safe bowl; Make sure the mixture is well mixed so the sugar can protect the eggs from cooking. Heat the mixture in the microwave for 2-4 minutes on high in 30 second intervals whisking well after each 30 second heating. Heat until the sugar is dissolved and the mixture reaches 160 f/72 C. Pour the syrup into a cake pan or shallow metal bowl (straining the mixture if any lumps are present) and chill in the freezer for 15-20 minutes until it is cool.
Meanwhile, beat the butter in a mixer for 2 minutes on high until the butter is lighter in color and aerated. Add the cooled syrup in two additions to the butter beating 1 minute after each addition. Add the vanilla and salt then beat 30 seconds until smooth; use immediately.

Chocolate: Add 300-525 g dark chocolate (70-77%), melted and cooled slightly, to the butter/syrup mixture.
Maple: Replace vanilla extract with 15 mL maple extract.
Peach: Replace vanilla extract with 15 mL crème de pêche.

You can store this buttercream at room temperature for 2 days, in the refrigerator, tightly sealed, for 2 weeks or in the freezer for 2 months.