In a medium saucepan (off the heat), whisk together the sugar, cornstarch, and Nescafé until evenly combined.
Gradually pour in the milk, whisking constantly to ensure a smooth mixture with no lumps.
Place the saucepan over medium heat. Stir continuously with a whisk or wooden spoon as the mixture begins to heat and thicken.
Once it starts to bubble and reaches a pudding-like consistency (about 5–7 minutes), add the chopped chocolate.
Stir until the chocolate is fully melted and the pudding is glossy and smooth.
Remove from heat and pour the mixture into serving cups or ramekins. Let cool slightly, then refrigerate for at least 1 hour before serving.
Optional: Dust with a pinch of Nescafé or cocoa powder before serving for a touch of flair.