01 - In a small saucepan over medium heat, combine heavy cream, sugar, cocoa powder, and salt. Whisk constantly until smooth and just beginning to simmer.
02 - Remove saucepan from heat, add chopped chocolate, and let sit for 1 minute. Whisk until chocolate fully melts and sauce becomes glossy and smooth.
03 - Stir in vanilla extract until evenly blended.
04 - Serve sauce warm over desserts. Rewarm gently if necessary before serving.