Add chopped chocolate to a microwave-safe bowl (or double boiler on the stove, stirring constantly) and melt the chocolate on half power, stirring ever 30-seconds, until melted and smooth.

Remove from microwave and stir in the sifted cocoa powder until smooth. The mixture will be thick. Set aside.

In a medium saucepan over medium heat, combine the sugar, corn syrup, cream, salt and water. Stir constantly and bring to a simmer. Simmer for 4 minutes. Remove from heat and stir in vanilla and butter.

Add the melted chocolate mixture then stir until smooth.

Serve warm, over ice cream for a hot fudge sundae, topped with whipped cream, sprinkles, and a cherry on top.