In a medium saucepan, whisk together egg yolks, milk, cream, sugar, cornstarch, cocoa, and salt until smooth. Bring to a boil over medium heat, whisking constantly; cook, whisking constantly, until mixture is thick enough to coat the back of a spoon, 3 to 4 minutes. Remove from heat, and stir in chocolate, butter, and vanilla until melted and smooth.
Pour mixture into a medium bowl, and cover with plastic wrap, pressing wrap on surface of custard to prevent a skin from forming. Refrigerate until thickened and cold, about 4 hours.
Recipe by Paula Deen Magazine at https://pauladeenmagazine.com/old-fashioned-chocolate-pudding/