Notes:

You can use any fruit pie filling if you prefer not to use apple pie filling.
You can also experiment with other spices like nutmeg, cloves, or allspice to customize the flavor.
Leftovers can be stored tightly covered in the refrigerator for up to 3 days.
To reheat, cover with foil and bake at 350°F for 15 minutes, or microwave individual pieces for 30-45 seconds.
If you don’t want to drizzle icing over the whole casserole, you can let each person drizzle their own icing.