Step 1 In a medium saucepan, combine 1 cup water with the sugar and corn syrup. Bring the mixture to a boil, stirring occasionally. Turn off the heat.
Step 2 Stir in the cocoa powder and chopped chocolate. Remove from heat and allow the chocolate to melt completely, whisking occasionally as it cools.
Step 3Strain the sauce and cool. (Whisk again before using.)