Put 115g of chopped semisweet chocolate, 6 tablespoons of granulated sugar, ½ cup of heavy cream, ¼ cup of light corn syrup, 3 tablespoons of unsweetened cocoa powder, and ⅛ teaspoon of salt in a medium saucepan.
Whisk over medium heat until the chocolate melts. Bring to a boil, whisking occasionally, and boil for 3 minutes, until it reaches 220°F / 104°C.
Remove from the heat and stir in 2 tablespoons of softened unsalted butter and 1 teaspoon of vanilla extract until smooth.
