Cut the bread into 1" chunks or cubes and spread them out evenly in an empty 21/2 quart casserole.
24 oz Brioche
Whisk together the eggs, milk, heavy cream, cinnamon, nutmeg, brown sugar, vanilla, and salt in a large mixing bowl.
7 large Eggs, ⅔ cup Heavy Cream, 1½ teaspoon Cinnamon, ½ teaspoon Nutmeg, 1½ teaspoon Vanilla extract, ½ cup Brown sugar, ¼ teaspoon Salt
Pour the custard over the bread cubes, ensuring all pieces are evenly coated.
Prepare the topping by mixing the additional brown sugar and cinnamon together in small mixing bowl. Cut in the butter until the mixture is coarse.
¼ cup Brown sugar, 1 teaspoon Cinnamon, 3 tablespoon Butter
Sprinkle the brown sugar cinnamon topping mixture over the top of the casserole.
Let casserole sit for at least 30 minutes, or preferably overnight, allowing the bread to absorb the custard.
Preheat the oven to 350°F. Cover the baking dish with foil and set in the center of the oven.
Bake the casserole for 20 minutes covered. Remove the foil and continue baking for another 30-35 minutes, or until golden brown and puffy.
Cool for 10 minutes before serving.