Preheat the oven to 325°F and lightly grease a 9 inch springform pan.
Place the digestive biscuits or graham crackers, 50 g of the granulated sugar, and 1/2 teaspoon of the cinnamon in a food processor and pulse into fine crumbs.
Add 60 g of the melted butter to the crumbs and pulse or stir until evenly moistened and the mixture clumps when pressed.
Press the crumb mixture firmly into the bottom of the prepared springform pan to form an even crust, then bake for 10 minutes and cool completely on a wire rack.
In a small bowl, combine 70 g dark brown sugar with the remaining 1/2 teaspoon cinnamon and set aside as the cinnamon sugar layer.
In another bowl, whisk the flour with 50 g dark brown sugar, then drizzle in the remaining 40 g melted butter and mix with a fork until coarse crumbs form; set aside as the crumble topping.
In a stand mixer bowl, beat the cream cheese on medium speed until completely smooth, scraping the bowl as needed.
Gradually add the remaining 100 g granulated sugar to the cream cheese and beat until the mixture is creamy and no graininess remains.
In a separate bowl, whisk together the sour cream and cornstarch until smooth, then mix this into the cream cheese along with the vanilla.
Add the eggs to the batter one at a time on low speed, mixing just until each egg is incorporated and the batter is smooth; do not overmix.
Wrap the outside of the springform pan with a layer of aluminum foil to protect it from water leaks.
Pour half of the cheesecake batter over the cooled crust and smooth the top with a spatula.
Sprinkle the cinnamon sugar mixture evenly over the batter, covering it from edge to edge.
Gently pour the remaining cheesecake batter over the cinnamon sugar layer and smooth the top without disturbing the layer beneath.
Sprinkle the crumb topping evenly over the surface of the cheesecake, leaving some larger clusters for texture.
Place the foil wrapped pan in a larger roasting pan and pour hot water into the roasting pan until it comes about halfway up the sides of the springform pan to create a water bath.
Transfer the pans to the oven and bake for 1 hour 15 minutes, or until the edges are set, the top looks matte, and the center has a slight wobble when gently shaken.
Turn off the oven, crack the door open, and let the cheesecake cool in the oven for 1 hour.
Remove the cheesecake from the water bath, discard the foil, and cool completely at room temperature on a wire rack.
Cover the cooled cheesecake and refrigerate for at least 8 hours or overnight before removing the springform ring, slicing, and serving.