Preheat your oven to 325°F (160°C). Blend the digestive biscuits and cinnamon until fine crumbs form. Add melted butter and pulse until combined. Firmly press the mixture into a 9-inch springform pan and bake for 10 minutes.

In a small bowl, mix dark brown sugar and cinnamon to create cinnamon sugar and set aside.

In another bowl, mix all-purpose flour with the remaining dark brown sugar. Pour in melted butter and mix until crumbly. Set aside.

Beat cream cheese on medium speed until smooth, then gradually add sugar. Blend in sour cream and cornstarch, followed by eggs one at a time until just incorporated.

Pour half of the cheesecake batter over the cooled crust, sprinkle with half of the cinnamon sugar mixture, add the remaining batter, and top with crumble.

Place the springform pan in a larger baking pan filled with boiling water. Bake for 1 hour and 15-20 minutes, until set around the edges.

Cool the cheesecake in the oven with the door ajar for 1 hour, then refrigerate for at least 6 hours or overnight.