Step 1

Place the chopped chocolate in a microwave-safe bowl and microwave in 30-second increments on 50% power, stirring after each, until the chocolate is melted and smooth. Set aside to cool to room temperature.

Step 2

Meanwhile, using the whisk attachment of your stand mixer, whip the butter on medium-high speed for 5 minutes, stopping to scrape the bowl once or twice.

Step 3

Reduce the speed to medium-low and gradually add the powdered sugar. Once all of the powdered sugar is incorporated, add the vanilla, mixing until incorporated. Add the melted chocolate and whip at medium-high speed until light and fluffy, about 2 minutes, scraping the bowl as needed to incorporate all of the chocolate.

Step 4

Use immediately or cover with plastic wrap and keep at room temperature for up to 4 hours before using. The frosting can be refrigerated, covered, for up to 4 days. Bring to room temperature and re-whip before using. The frosting can also be frozen in an airtight container for up to 3 months. Thaw in the refrigerator, then bring to room temperature before using.