Step 1

In a saucepan, whisk together the milk, sugar, cocoa powder, cornstarch, egg yolks, vanilla, and salt. Cook over medium-high heat whisking constantly, until the mixture comes to a simmer. Add the chocolate and butter.

Step 2

While continuing to constantly mix, bring to a full boil. Reduce the heat to maintain a simmer, and continue whisking until thick, about 2 or 3 minutes more.

Step 3

Pour the pudding into 6 small cups or ramekins. Place a piece of plastic wrap directly onto the pudding and refrigerate for at least 4 hours or until set.