Homemade Chocolate Pudding

Put 1 1/2 cups of the milk, the sugar, and the cocoa in a nonreactive saucepan. Bring to a simmer, over medium-high heat. Remove from the heat. Whisk the remaining 1/2 cup milk with cornstarch, salt, egg yolks, and vanilla in a bowl. Gradually whisk the hot milk into the egg mixture. Return to the saucepan and cook over medium-high heat whisking constantly, until the pudding comes to a full boil. Reduce the heat to maintain a simmer, and continue whisking until thick. (2 or 3 minutes) Pour the pudding into 6 small cups. Cover with plastic wrap and refrigerate for at least 4 hours or ideally overnight until set. Top with a bit of whip cream before serving.