In the bowl of stand mixer, combine the butter and salt. Beat the butter for 3 minutes, until very creamy.
While you beat the butter, melt the chocolate chips in a small microwave-safe bowl. Microwave for 30 seconds at a time, stirring after each microwave cycle. Repeat 2-3 times until the chocolate is melted and smooth.
Add ½ of the powdered sugar to the butter mixture and mix on low speed until combined.
Add the remaining powdered sugar. Mix on low speed until combined. Add the melted chocolate and mix on low speed until combined.
Add the cream and black food coloring, if using. Turn the mixer speed up to medium-high, and blend until the frosting is very fluffy—about 5 minutes.