Preheat your oven to 325°F (160°C). In a food processor, pulse the digestive biscuits and cinnamon until finely crushed. Pour in the melted butter and mix until fully combined. Press this mixture evenly into the bottom of a 9-inch springform pan. Bake for 10 minutes or until lightly golden, then allow it to cool.

In a small bowl, combine dark brown sugar and cinnamon; mix well and set aside.

In a mixing bowl, whisk together all-purpose flour and dark brown sugar. Pour in melted butter, mixing until the mixture becomes crumbly. Set aside.

In a stand mixer, beat the cream cheese until smooth and fluffy. Gradually add in sugar while mixing. In a separate bowl, combine sour cream and cornstarch, then gently fold this mixture into the cream cheese. Add vanilla extract, followed by eggs one at a time, mixing gently.

Carefully pour half of the prepared cheesecake batter over the cooled crust. Sprinkle evenly with the cinnamon sugar mix, then add the remaining batter on top. Finally, sprinkle the crumble topping generously over the surface.

Prepare a water bath by placing the springform pan into a larger pan filled with hot water up to about halfway up the sides. Bake for 1 hour and 15-20 minutes. The center should be slightly wobbly. Turn off the oven and let the cheesecake cool inside with the door ajar for about 1 hour.

Once cooled, transfer your Coffee Cake Cheesecake to the refrigerator and chill for at least 6 hours, or ideally overnight, to enhance the flavors.