Cocoa powder and unsweetened chocolate pair up in this chocolate dessert with a hint of cinnamon for a tasty flavor accent.
Stir together 2-3/4 cups of the milk and 1/2 cup of the sugar in a large saucepan. Heat until steaming. Remove from heat; set aside.
Once milk is warmed, whisk together remaining 1/4 cup sugar, the cornstarch, cocoa powder, cinnamon and salt in a medium-size bowl. Whisk in egg yolks and remaining 1/4 cup milk. Stir in a little of the hot milk mixture. Stir egg mixture into saucepan. Cook, stirring constantly with wooden spoon, over medium-low to medium heat until thickened and coats the back of a spoon, about 20 minutes. Remove from heat. Stir in the chopped chocolate, butter and vanilla until smooth.
Divide among six dishes, 2/3 cup in each. Cool 10 minutes. Cover with plastic wrap. Refrigerate at least 2 hours. Garnish with cookie, if desired.