Preheat the oven to 160?C (fan). Lightly grease an 8 x 8-inch baking pan and line with baking paper, ensuring plenty of overhang. Set aside.

Blitz the biscuits in a food processor or crush them in a bag until fine crumbs form. Stir in the melted butter until the mixture resembles damp sand. Press this mixture into the base of the prepared baking tin until smooth and even. Chill until needed.

In a bowl of an electric mixer, beat the cream cheese until smooth and fluffy. Add sugar, salt, and vanilla, mixing to combine. Add eggs one at a time, mixing well after each addition, scraping the sides of the bowl as needed.

Remove the crust from the fridge and pour the cheesecake batter over the chilled crust. Gently tap the baking tin to remove air bubbles.

In a large mixing bowl, combine the chopped apples with sugar, lemon zest, cinnamon, and nutmeg. Stir well and set aside for 5 minutes.

In a large mixing bowl, rub the chilled cubed butter into the flour, cinnamon, demerara sugar, and granulated sugar until the mixture resembles coarse breadcrumbs.

Top the cheesecake layer with the spiced apples, spreading them evenly. Sprinkle the crumble topping over the apples in an even layer.

Bake in the oven for 45-50 minutes, until the crumble is golden brown and the filling is set. Allow the cheesecake to cool completely on the kitchen counter. Once cooled, transfer to the fridge for at least 3 hours or ideally overnight.

Remove the cheesecake from the fridge using the overhanging baking paper to lift it out. Drizzle with caramel sauce, slice, and serve.