Preheat your oven to 325°F (160°C). Prepare an 8x8-inch baking dish by lining it with parchment paper, making sure to leave some overhang on the sides for easy lifting once baked.
In a medium-sized bowl, mix together the graham cracker crumbs, melted butter, and 2 tablespoons of granulated sugar. Stir until the mixture is evenly moistened and resembles wet sand.
Firmly press the crumb mixture into the bottom of the prepared baking dish to create an even and compact crust layer. Bake in the preheated oven for 10 minutes. Remove from the oven and let it cool slightly while preparing the filling.
In a large mixing bowl, use an electric mixer to beat the softened cream cheese on medium speed until it is smooth and creamy, which should take about 2-3 minutes.
Gradually add the 1 cup of granulated sugar, lemon zest, and freshly squeezed lemon juice to the cream cheese. Continue mixing on medium speed until everything is well combined and smooth.
Incorporate the eggs one at a time, mixing gently on low speed after each addition, just until combined. Be careful not to overmix, as this can create cracks in the cheesecake.
Using a rubber spatula, gently fold in the fresh blueberries and cornstarch, taking care to keep the berries intact.
Pour the cheesecake mixture over the cooled crust in the baking dish, spreading it evenly with a spatula.
Return the dish to the oven and bake for 30-35 minutes. The edges should be set while the center retains a slight jiggle; this indicates it will firm as it cools.
Allow the bars to cool in the pan at room temperature for approximately 1 hour. Then, refrigerate for at least 4 hours, or overnight if possible, to achieve the best texture and firmness.
Once fully chilled, lift the cheesecake out of the pan using the parchment overhang. Carefully cut into squares using a sharp knife.
Before serving, garnish each square with additional fresh blueberries on top.
Notes
Serve chilled with a light dusting of powdered sugar and a fresh mint sprig for garnish.