Preparation

1. In a medium saucepan, whisk together the cornstarch, cocoa powder, sugar salt, and salt.In a separate bowl, combine the milk and egg.Gradually pour the milk mixture into the saucepan, whisking until thoroughly mixed.
2. Heat the mixture, stirring constantly, over medium heat until it boils. Cook for 1 minute, then remove from heat.Stir in butter and vanilla extract.
3. Pour the pudding into the suitable molds rinsed with cold water (the pudding can be taken out more easily).Chill.