8sticks(4 cups) unsalted butterat room temperature
2teaspoonvanilla extract
Instructions
Whisk together egg whites and sugar in a heatproof mixing bowl over a pan of simmering water until sugar has dissolved, about 5 min. Test by rubbing the mixture between your fingers - you shouldn't feel any sugar crystals.
Transfer bowl to the mixer with a whisk attachment or use a handheld mixer and beat on high until it cools and stiff peaks form, 10 to 12 min.
Reduce speed to medium-high and add butter a few tablespoons at a time. (Buttercream may curdle but will become smooth as you continue to beat it.) Add Vanilla
Use within a few hours or refrigerate for u to a week. Buttercream can be frozen for up to a month. Before using, bring to room temperature and beat on low until smooth.
Notes
This is a double batch of meringue buttercream that is needed for larger projects like Party Rainbow Cake.