Preheat oven to 350ºF - place bread in a single layer on a baking sheet and allow to bake for 15 minutes until dry but not toasted - Remove from oven and allow to completely cool to room temperature - NOTE: You can use 2 day old brioche and skip this step; just leave the bread out with the wrapper open for 2 days before preparing
Place butter, brown sugar, and maple syrup in a small pan and heat over medium heat (stirring occasionally) until melted and smooth
Lightly grease an 8" X 13" baking sheet and spread the butter/sugar mixture evenly over the bottom of the pan
Place the bread slices in a single layer on top of the butter/sugar covering as much as possible
Beat the eggs in a medium bowl until just 'frothy (apx 1 minute) - Add the cream/half and half, vanilla extract/paste, salt, and cinnamon (if using) and whisk until thoroughly combined
Pour or spoon the egg mixture evenly over the bread slices - Cover and place in the refrigerator for a minimum 4 hours (overnight for better results
Place in a cold oven and set temperature for 350ºF - Once the oven reaches temperature, allow to bake until lightly golden (apx 25-30 minutes)
Flip the bread slices and continue to bake for 10 minutes - Change oven to broil and place the french toast 3-4 inches below the heating element - Allow to broil until the tops are nice and golden (apx 2-3 minutes)
Serve immediately with your favorite French toast toppings (powdered sugar, whipped cream, sliced fruit, fresh berries, etc), and syrup if you feel the need