Rich Chocolate Buttercream

Place the chocolate in a microwave-safe bowl and cook in the microwave in 20-second intervals, stirring in between, until it's about three-quarters of the way melted. Stir, allowing the residual heat in the bowl to melt the remaining chocolate completely. (If necessary, place the chocolate back in microwave for a few seconds.) Set aside to cool.

In a food processor, process the butter, confectioners’ sugar, cocoa powder and salt until smooth, about 30 seconds, scraping down the sides of the bowl as needed. Add the corn syrup and vanilla and process until just combined, 5 to 10 seconds. Scrape down the sides of the bowl, then add the lukewarm melted chocolate and pulse until smooth and creamy, 10 to 15 seconds. Do not overmix.

The frosting can be used immediately or held at room temperature for 3 to 4 hours. It may lose its shine as it sits—to bring the shine back, run a metal spoon under hot water, then wipe dry with a towel; stir the frosting with the hot spoon and it should shine right up.