Start by making the crust. Finely crush the digestive biscuits in a food processor. Melt the butter. Mix the cookie crumbs with the cinnamon and stir into the melted butter until you have a crumbly, sticky mixture. Press the mixture firmly into the bottom of a parchment-lined springform pan.
Next, make the cheesecake batter. In a bowl, beat the cream cheese with the sugar (180 grams/6.35 oz) until smooth and creamy. Add the eggs one at a time, mixing until each egg is fully incorporated.
Stir the vanilla extract into the sour cream and add it to the mixture. Add the flour and mix until the batter is smooth.
Peel and dice the apples into small pieces. Add the cinnamon and sugar (50 grams/1.76 oz) and mix well. Fold one-third of the apple mixture into the cheesecake batter.
Pour the batter over the crust and smooth the top with a spatula. Scatter the remaining apple pieces evenly over the cheesecake layer.
For the crumble topping, combine the butter, sugar, flour, and salt in a bowl. Rub together with your fingers until it forms a crumbly mixture. Sprinkle the crumble over the apples.
Bake the apple crumble cheesecake for 60 minutes at 300°F/150°C in a preheated oven (conventional top and bottom heat).
Turn off the oven and let the cheesecake cool inside the oven with the door slightly open.
Refrigerate the cheesecake overnight, or at least 6-8 hours, so it can fully set.
Serve with homemade caramel sauce.