For the Cookie Crust:
Preheat the oven to 160ºC (325ºF).
In a food processor, blend the digestive or graham crackers, brown sugar, cinnamon, and nutmeg until it resembles fine crumbs. Add the melted butter and blend again until combined.
Press the cookie mixture firmly into the bottom of a 22 cm (9-inch) springform pan, pushing it up the sides slightly.
Bake the crust for 10 minutes, then set aside to cool.
For the Apples and Crumble:
While the crust cools, dice the apples and toss them with granulated sugar and cinnamon. Set aside, draining any excess liquid before using.
In a separate bowl, mix together the flour, brown sugar, and butter until the mixture forms coarse crumbs. Set aside.
For the Cheesecake Filling:
Preheat the oven again to 160ºC (325ºF).
In a large bowl or stand mixer, beat the cream cheese on low speed for 1 minute. Gradually add the granulated sugar, mixing on low speed until smooth.
In a separate bowl, whisk together the sour cream and cornstarch until smooth. Add this to the cream cheese mixture along with the vanilla extract, mixing until combined.
Add the eggs one at a time, mixing on low speed after each addition until just combined.
Assembly and Baking:
Pour the cheesecake batter into the cooled cookie crust.
Gently scatter the cinnamon-coated apple cubes over the cheesecake, followed by an even layer of the crumble topping.
Prepare a water bath by placing the springform pan into a larger pan or wrapping the springform pan with triple layers of aluminum foil to prevent leaks. Place this in a larger roasting pan and fill it with hot water until it reaches about ⅔ up the side of the pan.
Bake for 1 hour 20-30 minutes. The cheesecake should still have a slight wobble in the center.
Cooling:
Once baked, turn off the oven and crack the oven door slightly. Let the cheesecake cool in the oven for 1 hour.
Afterward, remove it from the water bath and allow it to cool to room temperature for another hour.
Once completely cool, refrigerate the cheesecake for at least 6 hours, preferably overnight, before serving.