Spray a 9x13-inch baking pan with non-stick spray and set aside.
Cube the 1 (17.6-ounce) loaf brioche bread into 1-inch cubes. If brioche is pre-sliced, I recommend cutting each slice into 12 pieces.
Layer half of the bread into the pan.
In a medium bowl, stir together 8 ounces whipped cream cheese, ¼ cup powdered sugar, and 1 tablespoon vanilla bean paste until combined.
Then dollop half of the cream cheese mixture randomly over the top of the bread in the baking pan. I like to use a #100 scoop for this. Top with the remaining bread cubes and then dollop the rest of the cream cheese mixture on top.
*If you are adding 1 cup fresh fruit, 1 cup jam, 1 cup chopped nuts, or ½ cup chocolate chips, divide them in half and add them in layers with the cream cheese mixture. I recommend adding fruit OR jam, not both. The nuts and chocolate chips can be incorporated with fruit or jam or without.
In a medium bowl, whisk 8 large eggs, then add 2 cups half & half, ⅔ cup light brown sugar, ¼ cup 100% pure maple syrup, 1 tablespoon vanilla bean paste, ½ teaspoon ground cinnamon, and ¼ teaspoon salt. Whisk until combined.
Pour the egg mixture evenly over the top of the bread, then cover with aluminum foil and refrigerate overnight.
When ready to bake, preheat the oven to 350℉. Gently press the French toast casserole down with the aluminum foil to ensure even baking, then remove the foil.
Prepare the topping by cubing the 6 tablespoons salted butter and adding it to a medium bowl with ⅓ cup light brown sugar, ⅓ cup all-purpose flour, and ½ teaspoon ground cinnamon. Use your hand to mix it, pressing the butter between your fingers until all the ingredients are combined and clump together when pressed.
Sprinkle the topping over the bread and bake for 45 to 55 minutes. The lower end should yield a soft, casserole-like texture, and the higher end should produce a slightly less eggy texture.
Serve plain with a dusting of powdered sugar; can also add fresh fruit, maple syrup, or whipped cream.