In a large bowl combine milk, half-and-half, coffee powder, the 1 teaspoon cinnamon, and the ground chipotle chile pepper. If desired, cover bowl and chill for up to 24 hours.
Transfer mixture to a 3-1/2- or 4-quart slow cooker. Stir in chocolate pieces. Cover and cook on low-heat setting for 4 hours or on high-heat setting for 2 hours, whisking vigorously once halfway through cooking time. Serve immediately or keep warm on warm setting or low-heat setting for up to 2 hours.
Before serving, whisk well. To serve, ladle beverage into heatproof mugs or cups. If desired, garnish each serving with whipped cream and/or sprinkle with additional 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).