Slice 1 loaf of bread into small 1″ or 2″ pieces. Spray a 9″x13″ casserole dish with non-stick cooking spray. Set aside.
In a medium bowl, beat 8 large eggs. Next mix in 2 cups whipping cream, ¼ cup brown sugar, 2 tsp cinnamon, and 2 tsp vanilla extract.
Pour the liquid mixture into the casserole dish. Next add the bread chunks and spread evenly in the bottom of the casserole dish. Gently press the bread down so that it has fully soaked up the liquid like a sponge.
Cover with plastic wrap and let sit in the fridge for at least four hours, but preferably overnight.
After the bread has had time to soak, you can preheat the oven to 350°F.
MAKE TOPPING: In a medium bowl, mix together ½ cup brown sugar, ½ cup all purpose flour, and ½ Tbsp cinnamon.
Now add in ½ cup cold butter pieces. Using a pastry cutter or fork, crumble the butter into pea-sized pieces and mix everything together.
Take the casserole out of the fridge. The bread should have soaked up most of the liquid by this point. Now, pour the cinnamon butter crumble topping overtop of the casserole. Use a spatula to smooth it into an even layer.
Place uncovered in the oven to bake for 45-50 minutes or until it has reached the desired consistency (the more you bake, the less moist – so it depends on preference here). I cooked mine for 50 minutes.