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