Preheat your oven to 160°C (320°F). Line the base of a 20 cm springform pan with parchment paper and lightly grease the sides.

Crush the digestive biscuits in a food processor until fine crumbs form.

Melt 100 g unsalted butter, pour it into the biscuit crumbs, and mix until well combined.

Press the mixture firmly into the base of your prepared pan and bake for 10 minutes. Set aside to cool.

In a small saucepan, combine 200 g fresh blueberries, 50 g granulated sugar, 1 tbsp lemon juice, and 1 tbsp cornstarch stirred with a little water. Cook over medium heat until thickened, then remove from heat and let cool.

In a bowl, beat 600 g cream cheese with 150 g granulated sugar until smooth. Add the eggs, one at a time, mixing well after each addition.

Stir in 1 tsp vanilla extract and 100 g sour cream until the batter is creamy.

In another bowl, combine 50 g flour, 50 g oats, 50 g light brown sugar, and 50 g cold unsalted butter cut into small pieces. Rub together until coarse crumbs form.

Pour half of the cheesecake filling over the cooled crust, spoon half of the blueberry mixture over it, and gently swirl with a knife.

Sprinkle half of the crumble topping over the swirled layer, repeat with the remaining filling, blueberry mixture, and crumble.

Bake for 45 to 55 minutes until the edges are set but the center still has a slight wobble.

Turn off the oven, leave the cheesecake inside with the door ajar for 1 hour, then transfer to the fridge and chill for at least 4 hours, or overnight, before serving.