In a small pot, whisk together the milk, sugar, cocoa powder, and cornstarch. Place the pot over medium heat and cook until the mixture has thickened. Making sure to keep stirring to prevent the mixture from burning.

Place your egg yolks into a medium mixing bowl. Once the mixture has thickened, slowly whisk about ½ cup of the milk mixture into the egg yolks. Whisk the egg yolk mixture into the milk mixture.

Return the milk mixture to medium heat and cook the mixture For just one minute.

Remove the pudding from the heat and stir in the vanilla and butter. Whisk until the butter is well incorporated.

Pour the mixture into your serving bowl, cover the surface with plastic wrap, and make sure the plastic touches the pudding so it doesn’t form a film.