Make the crust: Crush the biscuits into fine crumbs using a food processor or a zip-top bag. Mix with melted butter until evenly moistened. Press firmly into the bottom of an 8-inch (20 cm) springform pan. Refrigerate while preparing the filling.

Prepare the blueberry puree (for the filling): In a small saucepan, combine blueberries, sugar, and lemon juice. Cook over medium heat until the berries soften and the sugar dissolves. Remove from heat and blend until smooth and let cool completely.

Bloom the gelatin: In a small bowl, mix gelatin powder with cold water. Let bloom for 10 minutes.

Make the cheesecake filling: In a large bowl, beat the cream cheese until smooth and creamy. Add powdered sugar and vanilla extract and mix until combined. Pour in the heavy cream and beat just until soft peaks form. Add the cooled blueberry puree and mix until smooth.

Temper the gelatin: Microwave the bloomed gelatin for 10–15 seconds, just until melted (do not boil). Temper by stirring a few tablespoons of the cheesecake mixture into it, then pour it back into the bowl and mix until fully incorporated.

Pour the filling over the crust and smooth the top.

Chill: Refrigerate (or freeze) for about 1 hour, until set enough to hold the topping.

Make the blueberry topping: In a small saucepan, mix the sugar and cornstarch. Add blueberries, lemon zest, lemon juice, and water. Cook over medium heat, stirring constantly, until the sauce thickens and the blueberries soften, about 5–7 minutes. Remove from heat and let cool slightly. Spread the topping evenly over the chilled cheesecake.

Final Chill: Refrigerate the cheesecake for at least 6 hours, preferably overnight, until fully set.