1. Prepare the Crust:

1. Before starting, preheat the oven to 160ºC/ 325ºF conventional oven. Prepare a 23 cm/9 inch springform tin lined with parchment paper in the bottom.
2. In a food processor, add the cookies and granulated sugar and blend it all together until a fine sand-like texture. Melt the butter. Add the melted butter to the food processor and blend it together with the blended cookies.
3. Add the cookie crumbs to the springform and press the cookie crumbs down with the bottom of a glass, and up against the side of the pan, so it’s well packed together and flattened out.
4. Bake it for 10 minutes. Then let it cool down so that it’s cool to touch. Keep the oven turned on.
5. While the crust bakes, prepare the blueberries and the crumble.
6. In a small bowl, mix together the blueberries, granulated sugar and all-purpose flour. Then add the lemon juice and mix it all together until there is no dry flour left. Set it aside.
7. For the crumble, add all-purpose flour and brown sugar to another bowl and mix it together. Melt the butter and pour it over the flour mixture. With a fork mix it together until it forms a crumbled structure and there is no dry flour left. Set aside both toppings while making the cheesecake filling.
8. With a hand mixer or in a stand mix using the paddle attachment, cream the cream cheese for 1 minute on low speed. Then add the granulated sugar and let it mix for 1 minute on low speed. Scrape down the side of bowl mix it together for another 30 seconds.
9. In a small bowl, mix together the sour cream and cornstarch until smooth. Add it to the cream cheese with the vanilla extract and let it mix on low speed until combined.
10. Then add two eggs at a time and let it mix on low speed until combined. Once all the eggs have mixed in, scrape down the sides of the bowl and give it a final mix to make sure all the ingredients have incorporated.
11. Pour the cheesecake batter into the spring pan. Gently divide the blueberries first on top of the cheesecake, followed by the crumble.
12. Boil up water in a kettle. Place the springform pan in a 30 cm/12 inch cake pan. Place the cake pan in another baking pan or roasting pan and fill it with hot water. This method will prevent water from getting into the crust.
13. Alternatively, add a triple layer of aluminium foil around the cake pan to safely seal it from the water before placing it in a water bath. There might be a possibility of water leaking in, so make sure it’s covered well if choosing this method.
14. Bake for 1 hour and 20-30 minutes.
15. Once the time has passed, give the tray a very gentle shake. The cheesecake should still be a small wobbly in the middle. Turn off the oven and have the oven door slightly open and let the cheesecake cool down in the oven for 1 hour.
16. Then take it out of the oven and remove it from the water bath and place the cheesecake on a cooling rack. Let it cool down fully for about 1 hour to room temperature.
17. Finally, once at room temperature, place it in the fridge and let it set for at least 6 hours, preferable overnight before eating.