Step 1

Bring cream, corn syrup* (See Notes below), brown sugar, cocoa powder, optional salt, and half the chopped chocolate to a boil in a 1 to 1 1/2-quart heavy saucepan over moderate heat, stirring, until chocolate is melted. Reduce heat and cook at a low boil for 5 minutes, stirring frequently.

Step 2

Turn off the heat and add butter, vanilla, remaining chocolate, and stir until smooth. Cool slightly before serving.

Step 3

Cooled sauce can be stored in a jar with a lid or in airtight container in the refrigerator for many weeks (recipe source says 1 week but I think that’s very conservative). I store mine for up to 1 week at room temperature; do as you’re comfortable with. Reheat sauce before using by placing the desired portion in a microwave-safe bowl and heating for about 10 to 15 seconds, or reheat on the stovetop.