For thw sauce
Combine the sugar, water, and corn syrup in a heavy bottomed saucepan and bring to a boil over medium-high heat. Remove from the heat. Place the cocoa powder in a bowl and add enough of the hot sugar syrup to make a paste, stirring until smooth. Gradually add the remaining syrup and mix until fully incorporated. Add the melted chocolate and blend until fully incorporated. Strain through a fine-mesh sieve. Serve warm or chilled.