Preheat oven to 375 degrees F. Spray a 9×9-inch baking dish with nonstick spray.

In a large bowl, whisk together oats, sugar, baking powder, salt and cinnamon. In a small bowl, whisk together milk, egg, and vanilla extract. Add the wet ingredients to the dry, stirring until combined. Stir in the mascarpone cheese, breaking it apart with a spoon but allowing it to remaining in chunks. Stir in the chocolate.

Pour in the baking dish and bake for 23-25 minutes, or until the the mixture is just set. The time may be a bit shorted or longer if you use a different sized baking dish. You don’t want to overbake it! Remove from the oven and serve immediately with extra milk for drizzling.