A fluffy, silky and smooth not-so-sweet meringue based buttercream, that is more stable than Swiss meringue buttercream but lighter in taste and texture. Perfect for all types of flavors and add ins.
Place the egg whites into the bowl of a stand mixer fitted with the whisk attachment.
In a heavy bottomed saucepan, combine the sugar and the water over medium-high heat. Stir to moisten the sugar.
Clip a candy thermometer to the side of the saucepan. Boil the sugar and water mixture. Do not stir.
Meanwhile, whisk the egg whites on medium speed until foamy, about 1 minute. Add the cream of tartar.
On medium speed, whisk the egg whites to soft peaks, about 1-2 minutes.
When the sugar syrup reaches 240F, remove the saucepan from the heat. Turn the speed of the mixer to high, and very carefully and slowly pour the hot syrup in a thin and steady stream into the bowl, pouring between the bowl and the whisk attachment so that the sugar syrup doesn't splatter. Don't rush.
Once the sugar syrup is added, continue to whip until stiff peaks form and the bowl is lukewarm to the touch, about 10-15 minutes. You can wrap the bowl with ice packs to speed up this process, if you wish.
Switch to the paddle attachment. With the mixer on low speed, add the softened butter, a few pieces at a time, mixing until the butter disappears into the meringue.
After all the butter has been added, increase the speed to medium and whip until thick, and fluffy.
Reduce the speed to low. Add the vanilla and salt, and beat for an additional 5-10 minutes to minimize the air bubbles.
Notes
Buttercream can be kept at room temperature for up to 2 days, refrigerated for 1 week in an airtight container and frozen for up to 3 months.
Keyword buttercream, frosting, italian meringue buttercream