In a 3 1/2- to 4-quart slow cooker, combine milk, half-and-half, chocolate pieces, coffee powder, 1 teaspoon cinnamon, and ground chipotle chile pepper.
Cover; cook on low-heat setting for 4 hours or on high-heat setting for 2 hours, whisking vigorously once halfway through cooking time. Whisk well before serving. If desired, garnish each serving with whipped cream and sprinkle with cinnamon.
Sweetened Whipped Cream
In a chilled mixing bowl combine whipping cream, sugar, and vanilla. Beat with an electric mixer on medium speed until soft peaks form (tips curl).