Chocolate Pudding

Whisk the sugar, cocoa, cornstarch, and salt in a heavy medium saucepan. Add half of the milk and whisk until the mixture is smooth. Whisk in the remaining milk. Continue whisking over medium heat until the pudding thickens and comes to boil, about 8 minutes. Continue to boil 1 minute longer, whisking constantly.

Remove the pudding from the heat. Add the chopped chocolate and vanilla; whisk until the chocolate melts and the pudding is smooth. Pour the pudding into a medium bowl and place a piece of plastic wrap directly over the pudding to prevent a film from forming at the top. Cool in the refrigerator until set, 5 to 6 hours. Whisk the chilled pudding until smooth, and then spoon it evenly into 4 dessert bowls. Top each pudding with a dollop of whipped cream, if desired, and serve.