Melt butter, sugar and a pinch of salt in a saucepan.
Add chopped dark chocolate.
Sift in the cornstarch until you get a smooth pasty consistency.
Gradually pour in the milk while continuously whisking to create a smooth mixture.
Cook until it thickens for about 5 minutes.
Pour the pudding into slightly oiled individual serving dishes or a large bowl. Let it cool at room temperature for a bit before refrigerating.
Cover the pudding with plastic wrap, making sure it touches the surface to prevent a skin from forming. Refrigerate for at least 2 hours, or until it's completely chilled and set.
Once the pudding is chilled, you can serve it as is or with a topping of your choice. Cocoa powder, whipped cream, chocolate shavings, or fresh berries are great options.