Start with the butter! Before adding anything else to the mixer, whisk the softened butter for 7 to 8 minutes, until it's super fluffy and pale white in color and don't forget to scrape down the sides of the mixing bowl often. Only then start adding the chocolate and sugar.
Melt the chocolate chips in the microwave or over a double boiler until smooth. Allow the chocolate to cool until it's just lukewarm. Next, add in the melted chocolate to the butter and whisk again for about a minute, until the chocolate is well incorporated.
Next, add in the confectioner's sugar, cocoa powder, salt and vanilla extract. Mix on slow speed first, then turn the mixer to high and mix for 3 to 4 minutes, until the frosting is fluffy. Scrap down the sides of the mixing bowl to ensure everything gets incorporated.