Preheat oven to 350°F (177°C). Line a 9-inch square baking pan with parchment paper with enough overhang on the sides to easily lift the chilled bars out as a whole. Set aside.

If you’re starting out with full graham crackers, use a food processor or blender to grind them into fine crumbs. You can also place them in a zip-top bag and crush them into fine crumbs with a little arm muscle and a rolling pin. Stir the graham cracker crumbs and granulated sugar together in a medium bowl, and then stir in the melted butter. The mixture will be thick, coarse, and sandy. Try to smash/break up any large chunks. Press into the bottom of the lined pan.

Bake the crust for 8 minutes. Cool for a few minutes as you prepare the filling in the next step.

Using a handheld or stand mixer fitted with a paddle attachment, beat the cream cheese for 1 minute on medium speed until smooth. On medium speed, beat in the egg, sugar, lemon zest, lemon juice, and vanilla extract together until smooth and creamy, about 3 full minutes. Gently fold in the blueberries. Pour/spoon filling evenly onto the warm crust.

Bake for 30–35 minutes, or until the cheesecake has set up and the edges are lightly browned. The bars will be very puffy, but will sink down slightly as they cool. Remove from the oven and allow to cool for 30 minutes at room temperature on a wire rack and then chill in the refrigerator for at least 3 hours.

Lift the parchment paper out of the pan and cut into squares.

The bars stay fresh in an airtight container in the refrigerator for up to 5 days.