You will need a double boiler or makeshift double boiler for this recipe. I use my KitchenAid stand mixer and a medium-sized saucepan that the bowl fits snugly into without touching the bottom of the pot.

In clean, dry mixer bowl, combine egg whites, sugar, and salt and whisk until combined.

Heat about 1 ½ inches of water over medium-low heat in a medium-sized saucepan and bring to a simmer. Rest the bowl of your mixer in the pot over the simmering water (should not be touching the water).

Whisk egg white/sugar/salt mixture constantly until the sugar is dissolved and mixture is no longer grainy (if you rub a small bit between your fingers it should feel smooth and not at all gritty) and the mixture reaches 160F (70C). This will take several minutes.

Remove mixing bowl from heat and dry the bottom of your bowl. Fit bowl into your stand mixer.

Using a whisk attachment, beat the egg whites on medium/medium-high speed until meringue is thick and glossy and you have achieved stiff peaks (see photo in post or see video for visual). This will take about 10 minutes or so.

Once you have achieved stiff peaks, stop beating and allow bowl to cool down completely. The bowl must no longer be warm to the touch before proceeding.

Once bowl is no longer warm to the touch (make sure you are feeling near the bottom of the bowl), switch out whisk attachment for paddle attachment. Turn mixer to medium speed and add butter one Tablespoon at a time. Don’t add the next tablespoon of butter until the previous one is incorporated into the meringue. If you notice that your buttercream starts to break down or look curdled, just keep mixing and it will come together. If it still doesn’t come together (it could take some time), place the mixer bowl in the fridge for about 10 minutes and then try mixing again.

Once all butter has been beaten into the meringue, scrape down the sides of the bowl and stir again. Beat on medium/high until smooth and thick.

Stir in vanilla extract or other flavoring and any food coloring, if using.

Spread or pipe over cupcakes or cake or use under fondant! I used an Ateco 848 for the cupcakes shown in this post.