Using a sharp serrated knife, carefully cut a pocket in each slice of bread. The pocket should be on the bottom edge of each slice and should go up about 2 inches.
In a bowl combine the mascarpone, brown sugar, and cinnamon. Mix until smooth. Scoop a small amount of the mixture into the pocket of each slice of bread. Gently press the seam together so it is mostly sealed.
In a shallow dish, combine the milk, eggs, and cinnamon. Whisk until combined. Briefly dip each piece of stuffed bread into the egg mixture on both sides.
Transfer to a greased pan over medium heat. Cook for about a minute on both sides until golden brown. Top with fresh berries and whipped cream, and whatever other toppings you like! Enjoy!