Prepare the crust
1-In a bowl, stir together graham cracker: In a bowl, stir together graham cracker crumbs and sugar. Add melted butter and whisk with a fork until everything is evenly moistened and resembles wet sand. Press the mixture firmly into the bottom of the pan. Place in the fridge to chill while you prepare the filling.

Make the crumb topping
2-In a bowl, stir together flour, granulated: In a bowl, stir together flour, granulated sugar, and brown sugar. Add melted butter and mix until coarse crumbs form. Place in the fridge.

Make the cheesecake filling
3-Beat softened cream cheese, sugar, and vanilla: Beat softened cream cheese, sugar, and vanilla until smooth. Add sour cream and cornstarch, mixing until combined. Add eggs and mix just until incorporated. Do not overmix.

Prepare the blueberry filling
4-In a bowl, lightly mash about 3: In a bowl, lightly mash about 3 – 4 tablespoons of the blueberries with a fork. Add the remaining blueberries, lemon juice, sugar, and cornstarch, then stir until evenly combined.

Assemble and Bake
5-Spread the cheesecake filling evenly over the: Spread the cheesecake filling evenly over the chilled crust. Spoon the blueberry mixture on top and gently spread it out. Sprinkle the crumb topping evenly over the blueberries.
6-Bake for about 45-55 minutes, or until: Bake for about 45-55 minutes, or until the center is set. Start checking after 35 minutes and tent with foil if the top is browning too quickly. The bars will puff up slightly while baking, then settle as they cool.
7-Let the bars cool in the pan: Let the bars cool in the pan for about 30 minutes, then lift them out using the parchment overhang. Cool completely, then refrigerate for at least a few hours before slicing.