For the apples, melt the butter in a large skillet over medium heat. Add in the diced apples, maple syrup, cinnamon, allspice and salt. Stir to combine. Cook the apples for 4-5 minutes or until just tender, stir often.

In a large bowl whisk together the eggs, egg whites, milk, maple syrup, vanilla, cinnamon, allspice and salt.

Place half of the bread cubes into the prepared baking dish. Sprinkle half of the apples and cranberries evenly over the bread. Repeat these steps with the remaining ingredients. Pour the egg mixture evenly over the casserole.

Use your hands to press the bread down so that it's coated in the egg mixture. Cover with plastic wrap or foil and refrigerate for 2 hours or overnight.

Remove the casserole from refrigerator and let it come to room temperature, about 30 minutes. While the casserole comes to room temperature preheat oven to 350° F. Cover the casserole with foil and bake on the middle rack of the oven for 50-60 minutes. Remove the foil and bake another 10-15 minutes or until the top is lightly browned and the center is firm.

Just before serving whisk together the ingredients for the vanilla glaze. Serve the casserole with maple syrup and drizzled with the vanilla glaze if desired.