Preheat the oven to (180C or 160C on a fan-forced oven).
Wrap the outside of a 9-inch (23-cm) springform pan in tin foil so that the bottom and sides are covered. Wrap it at least 3-4 times so that all the seams are covered too. Lightly grease the pan with non-stick cooking spray.
Mix the graham crumbs, brown sugar and cinnamon. Then mix in the melted butter
Press the mixture into the bottom and about 1/2 way up the sides of the pan.
Bake in the preheated oven for 8-10 minutes. Remove from the oven and keep the oven turned on.
Peel and core the apples. Slice into very thin slices.
Toss the apples with the brown sugar and cinnamon. Place in the fridge until you'll need them later.
Stir together the flour, brown sugar and cinnamon in a medium bowl until no lumps remain. Then mix in the oats.
Stir in the melted butter. It should look like damp sand and form clumps/crumbles if you squeeze it in your palm. Set aside until you'll use it later.
In a very large bowl, beat the cream cheese and sugars until smooth and creamy. Turn off the mixer and scrape down the sides and bottom of the bowl as needed.
Mix in the corn starch and cinnamon. Then mix in the sour cream and vanilla extract. Again, turn off the mixer and scrape down the bowl to ensure there are no lumps of cream cheese.
Mix in the eggs 1 at a time. Stop mixing as soon as the eggs are combined. You should no longer see pieces of egg yolk or egg white.
With the pan still wrapped in foil, pour the cheesecake filling over the crust and smooth the top.
Place sliced apples on top of the cheesecake in an even layer. Do not add any juice/liquid from the bottom of the bowl of your apples. You may not quite need all the apples to form an even layer.
Sprinkle the oatmeal crumble mixture over the sliced apples. It may look like quite a bit, but it really isn't after the cheesecake is baked.
Place the cheesecake inside a large roasting pan (the pan should still be wrapped in foil).
Pour boiling water into the roasting pan so that there's about 1 inch of water in the pan.
Place the roasting pan in the oven. Bake the cheesecake for about 50-60 minutes. When it's done baking, there should be a very slight wobble if you gently nudge the pan.
Remove the cheesecake from the oven. Cool in the roasting pan until it reaches room temperature.
Remove the cheesecake from the roasting pan. Cover the pan with tin foil and place in the fridge to set for at least 6 hours or overnight.
When ready to serve, remove the cheesecake from the fridge.
Trace around the edges with a sharp knife. Then unclamp the outer ring of the springform pan.
Slice the cheesecake using a thin, sharp knife (not a table knife). Be sure to slice all the way through the crust. This recipe can be a little messy to slice, so don't worry if your pieces don't look perfect.
Optionally, drizzle each piece with a little salted caramel.
