Make the Blueberry Curd In a small saucepan, combine the blueberries, sugar, water, and lemon juice. Bring to a gentle simmer over medium heat and let it cook for 5–7 minutes, stirring occasionally and gently mashing the berries. In a small bowl, stir the cornstarch with a splash of cold water, then stir it into the blueberry mix. Cook for another minute until slightly thickened. Remove from heat and let it cool completely.
Make the Base Crush the Digestive biscuits until fine, then mix them with melted butter until it resembles wet sand. Press the mixture firmly into the bottom and slightly up the sides of a 20 cm (8-inch) springform pan. Chill in the fridge while preparing the filling.
Make the Cheesecake Filling In a large bowl, mix the cream cheese, powdered sugar, vanilla, and melted Biscoff until smooth. In a separate bowl, whip the heavy cream until soft peaks form. Gently fold the whipped cream into the cream cheese mixture until fully combined and fluffy.
Assemble Pour half of the cheesecake filling into the chilled crust and smooth it out. Spoon over the cooled blueberry curd in an even layer. Add the rest of the cheesecake filling and smooth out the top. Tap the pan gently on the counter to level everything.
Chill Cover and freeze for at least 1,5 hour, until fully set.
Flip & Serve Once set, place a serving plate over the cheesecake and flip it upside down (you can use parchment paper to help if needed). Gently remove the springform pan. The crust will now be on top, and the creamy cheesecake with blueberry curd underneath. Slice and serve!