Add the egg whites and sugar to the bowl of your mixer.

Cut butter into small pieces. It needs to be very soft, so let it sit out for about an hour before you begin to make the buttercream.

Place the bowl over a pan of simmering water. Whisk constantly until the sugar dissolves into the egg whites.

It takes about 5-10 minutes, and you will know that it is ready when you don't feel any sugar granules when you rub it between your fingers. You will also no longer see sugar granules on the side of the bowl. If you are really unsure, you can use a candy thermometer and when the mixture reaches 160° it is ready.

Add the mixing bowl to the mixer fitted with the whisk attachment. Mix on low speed so that it doesn't splash on you, then slowly increase speed to high. Let mix for 10 minutes, or until the bowl of the mixer is no longer warm to the touch. If it is too hot, it will melt your butter.

Add the vanilla, almond extract, and salt.

When all of your butter is added, it's going to look a little sad. Don't worry. It's going to be just fine. Continue to whisk on high speed until thickened, glossy, and smooth.