Caramelize the pears in butter until soft and golden brown. Add in spices and ¼ c of the brown sugar then set aside.
In a large bowl, whisk together the eggs, milk, vanilla extract, and cinnamon.
Dice the challah into small pieces and layer into an oven-safe baking dish.
Pour egg mixture over the entire challah, making sure each cube of bread is soaked with the egg mixture. Then, pour the caramelized pears on top of the soggy brioche.
Sprinkle the remaining brown sugar on top of the bread mixture. Bake at 375°for 20-22m.