How to make the most amazing frosting - Swiss Meringue Buttercream!
Note: You really need an ELECTRIC MIXER for this recipe.
Place egg whites and sugar in a large bowl (I used the Kitchenaid bowl that comes with the mixer). Whisk until combined. Place the bowl over a pot of simmering water and whisk like crazy for 2 minutes or until the sugar has dissolved. DO NOT STOP whisking or you will have scramble eggs. Remove from heat and beat on high for 20 minutes with the whisk attachment of your mixer.
Once your egg whites and sugar mixture have been beaten for 20 minutes, you should have stiff peaks of meringue that has just about come to room temperature. Now you're ready for the butter. With the mixer on low, add your butter 2-3 tablespoons at a time. Once you've completely incorporated all the butter, then add your vanilla extract and flavoring. Mix until combined. Your mixture will be a bit soupy at this point, so you will need to refrigerate for 2 hours or overnight.
After the buttercream has been chilled, take it out of the refrigerator and let it sit for an hour or so. You don't want it TOO cold. I know, this is a bit fussy, but I promise it's worth it. Now you can beat your buttercream again on medium high and watch the magic. At first it might look sort of curdled but don't worry, just keep beating it. After a few minutes, it will turn into a light and fluffy buttercream. This could take anywhere from 1-4 minutes. Now you're ready to frost your cake or cupcakes.
This recipe makes enought buttercream to fill and frost a 9-inch round cake (3 layers) or 24 cupcakes. Store covered. Let it come to room temperature before serving. You will need to beat it to make it light and fluffy again.
It's a good idea to make the Swiss Meringue Buttercream ONE DAY AHEAD as it should be refrigerated over night for best results.