Combine brown sugar, flour, water and cinnamon in a medium bowl. Add softened butter and knead into the sugar mixture with your finger tips. When completely moistened, set aside.
Place rack in the center of the oven then preheat to 375 degrees.
Grease a 9" × 13" casserole dish then add shredded bread. Make sure to cover the entire bottom of the dish evenly then set aside.
In a medium-sized mixing bowl, whisk eggs then add milk, vanilla and salt. Pour mixture over bread then set aside.
In a large skillet over medium heat, combine butter and apples. Stir ingredients until they are evenly coated then cover pan to let the apples steam and soften for about 3–5 minutes, stirring occasionally. Uncover then stir in cinnamon and brown sugar. Continue cooking until tender and caramelized—about 3 minutes.
Next, carefully pour apples into a casserole dish on top of shredded bread. Using a wooden spoon, gently push ingredients around to distribute evenly.
Sprinkle topping mixture over casserole. Bake for 45 minutes, or until nicely browned on top. Remove from the oven then top with maple syrup or powdered sugar. Enjoy!
Notes
You can make this recipe up to 24 hours in advance then bake it fresh!