Heat the oven to 425 F and butter a 1-quart baking dish.
Put the bread in the baking dish.
Melt the butter and brown sugar in a small saucepan over medium-low heat and stir until smooth. Set aside to cool slightly. Whisk the eggs and milk together in a medium bowl. Add the vanilla and cinnamon and mix well. Whisk in the cooled brown sugar mixture.
Pour the egg and milk mixture over the bread and press the bread gently to saturate the cubes.
Drizzle a tablespoon or two of maple syrup over the mixture and bake the casserole for 25 minutes or until browned and puffy.