2teaspoonvanilla extract, I swapped this for hazelnut extract
Instructions
Place the egg whites and sugar in the bowl of a stand mixer fitted with the whisk attachment and stir on low until the sugar is just blended with the egg whites.
Place the bowl over a saucepan of simmering water (make sure the water does not touch the base of the mixer bowl) and stir frequently until the sugar dissolves. When your thermometer reaches 140°F to 150°F, take it off the saucepan.
Transfer the bowl to the mixer and beat on high speed until the meringue and the bowl are cool to the touch.
Add the cubed butter gradually, mixing after each addition until fully incorporated and scraping down the sides of the bowl as needed. Blend in the extract.
The buttercream is ready to use now or may be tightly covered and stored in the refrigerator for up to 1 week. It can also be frozen for up to 1 month.