0 To a small saucepan, add the chopped chocolate bar, granulated sugar, heavy whipping cream, light corn syrup, sifted black cocoa powder, and salt.
1 Continually stir and heat the mixture over medium heat until it reaches [wprm-temperature value="200" unit="F"].ELIZABETH'S NOTE: For an extra thick hot fudge sauce, heat it up to [wprm-temperature value="220" unit="F"] (but not beyond).
2 Remove from heat. Add and stir in the cubed unsalted butter and vanilla extract.
3 Serve immediately or allow it to cool to desired consistency. Storing information in recipe notes below.