Overnight Pumpkin French Toast Casserole

Spray a 13x9 glass pan with cooking spray and evenly spread out the cubed brioche bread in the pan. Set it aside.
In a medium-sized bowl, whisk together the pumpkin puree (1 cup), light brown sugar (½ cup), cane sugar (¼ cup), eggs (6), milk (1 cup), vanilla extract (1 Tbsp), and pumpkin pie spice (2 ½ tsp) until smooth. Evenly pour the pumpkin mixture over the top of the cubed bread.
Gently toss the cubed bread with either a rubber spatula or your hands to get the majority of the bread covered in the pumpkin mixture. Don't overmix it--squishing the bread too much will make the casserole dense.
Cover the 13x9 glass pan and put it in the refrigerator to sit overnight, or at least a few hours.
For the crumble topping, stir together the all purpose flour (½ cup), brown sugar (½ cup), pumpkin pie spice (½ tsp), and old fashioned oats (½ cups) in a small bowl. Add the cubed butter, and stir until the butter is coated. Then use your hands to manipulate the topping until there aren't any more chunks of butter. Cover and refrigerate until ready to bake.
When you are ready to bake the french toast casserole, preheat the oven to 350° F. Take the casserole and the topping out of the refrigerator, and break up the topping into small pieces, spreading it over the top of the casserole.
Bake for about 30-40 minutes, or until the crumble topping starts to brown.
Serve with your favorite kind of syrup--I recommend buttermilk syrup.
Enjoy!