01 - In a medium saucepan, whisk together sugar, cocoa powder, cornstarch, and salt.
02 - Gradually whisk in the milk to dissolve the dry ingredients completely.
03 - Place the saucepan over medium heat and cook, whisking constantly, until the mixture thickens and begins to bubble, about 5 to 7 minutes.
04 - Remove from heat, then stir in the chopped chocolate and vanilla extract until the chocolate is fully melted and the mixture is smooth.
05 - Pour the pudding into 4 serving dishes. Let cool slightly, then cover with plastic wrap pressed directly onto the surface to prevent a skin from forming.
06 - Refrigerate for at least 1 hour or until fully chilled.
07 - In a chilled bowl, beat heavy cream, powdered sugar, and vanilla extract until soft peaks form.
08 - Top the chilled pudding with a generous dollop of whipped cream before serving.