In a saucepan, combine cored and peeled apples, brown sugar, cinnamon, nutmeg, lemon juice, and water. Cook over medium heat until the apples soften, about 10 minutes. Mix in cornstarch and cook until the mixture thickens. Set aside to cool.

In a bowl, mix graham cracker crumbs, melted butter, and granulated sugar. Press this mixture firmly into the bottom of a springform pan. Set aside.

In a large mixing bowl, beat cream cheese until smooth. Gradually add granulated sugar, eggs, vanilla extract, and sour cream, mixing well after each addition. Stir in cornstarch and mix until everything just comes together.

In another bowl, combine oats, flour, brown sugar, butter, and cinnamon until crumbly. Don’t stress about it being too perfect; lumps are okay!

Pour the cheesecake filling over the crust, followed by the cooled apple mixture, and finally sprinkle on the crumble topping. Bake the whole thing for around 60-70 minutes at 325°F (160°C) until the center is set. Let it cool before removing it from the pan.