Step 1

Heat the oven to 350°F. Line the bottom and sides of an 8x8-inch square metal baking pan (about 2 inches tall) with 2 sheets of parchment paper, positioning them perpendicular to each other and making sure they are long enough to hang over all four sides by at least 1 inch to form a sling.

Step 2

Break 16 whole graham cracker sheets into rough pieces and place in a food processor. Add 1/4 cup granulated sugar and 1/4 teaspoon of the kosher salt. Process until the crackers are the texture of sand, about 15 seconds.

Step 3

Add 9 tablespoons melted unsalted butter and pulse to combine, 8 to 10 (1-second) pulses. (If using graham cracker crumbs, just stir the crumbs and butter together in a medium bowl.) Reserve 2/3 cup of the mixture for topping.

Step 4

Transfer the remaining mixture to the baking pan. Use the bottom of a flat measuring cup or your fingers to press the crumbs into an even layer, making sure to reach the edges and fill the corners.

Step 5

Bake until fragrant and starting to darken around the edges, 12 to 15 to minutes. Let cool slightly while you prepare the filling.

Step 6

Wipe the food processor clean with paper towels. Place 16 ounces room-temperature cream cheese in the food processor. Process until very smooth and fluffy, 1 to 2 minutes. Scrape down the sides of the bowl.

Step 7

Add 1/2 cup granulated sugar, 2 teaspoons finely grated lemon zest, 3 tablespoons lemon juice,1 teaspoon vanilla extract, and 1/4 teaspoon kosher salt. Process until combined, about 30 seconds. Scrape down the sides of the bowl. With the motor running, add 2 room-temperature large eggs one at a time and process until just incorporated.

Step 8

Remove the blade. Add 1 1/2 cups of the blueberries into the food processor bowl and gently stir to combine. Transfer to the graham cracker crust and spread into an even layer. Scatter the remaining 1/2 cup blueberries over the top. Sprinkle with the reserved crumb mixture.

Step 9

Bake until the edges are set and puffed and the center is still slightly jiggly, 30 to 35 minutes. Place the pan on a wire rack and let cool completely, about 2 hours. Cover and refrigerate until chilled, at least 3 hours or up to overnight.

Step 10

Grasping the excess parchment, lift the slab out of the pan and place on a cutting board. Dust with powdered sugar if using. Cut into 9 or 12 bars.