In a medium sized mixing bowl , mix 6 large eggs, 1 cup half and half, 1 cup 2% milk, ½ cup granulated sugar, 2 teaspoons vanilla, and 1 teaspoon cinnamon together. Set aside.
Spray a 9x13 inch pan with cooking spray and place half of the 1 (16-ounce) cubed loaf challah bread in the bottom. Layer with half the 3 Granny Smith apples peeled and sliced thin and pour about a third of the egg mixture over it. Repeat again with the remaining bread, apples, and mixture. Cover with plastic wrap and place in the fridge overnight or for at least 4 hours.
For the Streusel:
Mix ⅓ cup light brown sugar, ⅓ cup all-purpose flour, and 1 teaspoon cinnamon together. Using a fork or pastry blender, mix ¼ cup diced unsalted cold butter into the flour mixture until the dough has a coarse crumb-like texture.
Preheat oven to 350 degrees Fahrenheit and take the casserole out of the fridge. Sprinkle with the streusel topping and bake for 45-55 minutes. Let cool for 5-10 minutes before slicing. Serve with powdered sugar and maple syrup.