1. Preheat oven to 350º F and lightly grease a 12-piece muffin tin.
2. Place the bread cubes into a large bowl.
3. In a medium-sized bowl, whisk together the milk (2 cups), (6) eggs, vanilla (2 teaspoons), brown sugar (4 Tablespoons), and cinnamon (2 teaspoon) until well combined. Fold in the grated apple (2 cups).
4. Pour the wet mixture over the bread cubes and toss to evenly coat them; set aside to soak while you make the crumb topping.
5. To make the crumb topping, mix the flour (1/2 cup), brown sugar (1 Tablespoon), cinnamon (1 teaspoon), and salt (1/8 teaspoon) in a medium-sized bowl. Add the cold butter cubes (½ cold stick butter) to the flour mixture and, with your hands, mix the butter in until the flour turns into a crumb-like texture.
6. Carefully fill the muffin tin with the soaked bread cubes, packing them gently to the top. Sprinkle the crumb topping evenly over each muffin.
7. Bake the muffins for 20-25 minutes or until they’re golden and baked through the middle.
8. When ready, remove them from the oven and let them sit for about 5 minutes before digging in.
9. Serve them warm with a drizzle of maple syrup.