In large pot, combine sugar, cocoa, salt, and water. Whisk until smooth. Set aside.
Place the cornstarch, chocolate, and vanilla in larger bowl and set aside.
Once the milk has come to a scald, remove from the heat and set aside.
Place the pot with the sugar-water mixture over moderately-high heat and bring to a boil, whisking frequently. Remove from heat and add the chopped chocolate. Whisk until thoroughly melted. Set aside.
In the cornstarch bowl, whisk enough of the hot milk with the cornstarch to make a slurry, then whisk in the remaining milk.
Pour the milk into the chocolate mixture, then return to moderately-high heat.
Cook the pudding until it reaches the boil. Stirring with a heatproof spatula, making sure to continuously scrape the bottom of the pan. Allow to boil for 1 minute, still scraping the bottom of the pan. Remove from the heat and whisk in the vanilla.
Immediately pour the pudding into a pan and press plastic wrap snugly against the surface.
Refrigerate for several hours. Spoon pudding into bowls and top with fresh whipped cream.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.