Step 1

Combine the whites, powdered sugar, and salt in the bowl of a large stand mixer fitted with a paddle attachment. Mix everything together on low speed, until the sugar is moistened and no dry patches remain. Turn off the mixer, scrape down the sides and bottom of the bowl with a spatula, then turn the mixer to medium speed. Beat on medium for 5 minutes.

Step 2

After 5 minutes, turn the mixer to medium-low and start adding the softened room temperature butter, 1-2 tablespoons at a time. Once all of the butter is incorporated, add the vanilla extract and mix it in. Stop the mixer and scrape down the bottom and sides once more. Turn the speed to medium and beat the buttercream for 10 minutes. At the end, you’ll have a frosting with a wonderfully light and creamy texture. It can be used right away, or stored in the refrigerator for up to two weeks, or the freezer for up to two months. If you have chilled the frosting, let it come to room temperature and then beat it for several minutes to smooth it out and restore its texture before using it.

Step 3

To make chocolate buttercream, chop 12 oz unsweetened chocolate, and place it in a microwave-safe bowl. Microwave in 30-second increments, stirring after every 30 seconds to prevent overheating. Once the chocolate is melted, let it cool until it is completely room temperature. Make the frosting as described, and after it is finished, add the melted and cooled chocolate. Mix on low speed until the chocolate is completely incorporated.