Spray or butter an 8-inch square pan. If you want to line the pan, use a piece of parchment paper covering the bottom and two sides. You will have two sides without paper. It makes it easier to remove the cheesecake when it's cold; you lift the paper and take out the block of cheesecake.
Stir 1 cup ground graham crackers in a bowl with ¼ cup unsalted butter, melted, until the mixture looks like wet sand. If you have whole cookies, use the food processor to grind them, add the melted butter, and pulse to mix.
Dump this mixture into the prepared baking pan and press firmly onto the bottom. Bake for 10 minutes. Remove from the oven and let cool on a wire rack while preparing the filling.
Lower the oven to 325°F (170°C).
Blueberry cream cheese filling:
Mix 16 ounces regular cream cheese, softened, in a large bowl until very smooth. You can use a handheld mixer or a wire whisk. Mixing the cheese by hand should not be a problem if the cheese is at room temperature. If using an electric mixer, use it only for this part and at the lowest speed. We don't want to incorporate air into the batter.
Gradually add ½ cup + 2 tablespoons granulated sugar and beat until it's very well incorporated.
Add 3 eggs all together, mixing until incorporated and scraping down the sides of the bowl to make sure all the ingredients are well mixed. Don't be tempted to beat.
Add ½ teaspoon vanilla extract or vanilla paste, ½ teaspoon lemon zest and ¼ cup sour cream, stirring to incorporate.
Add 1 ½ cups blueberries to the cream cheese mixture and stir with a spatula. Don't crush the berries. Pour the batter into the prepared pan.
Bake the cheesecake for about 30 to 35 minutes, until the center jiggles slightly and the sides are a little puffed. The time can vary depending on your oven.
Remove from the oven, let it cool on a wire rack for 15 minutes, and carefully run a smooth-bladed knife around the sides of the pan to loosen up any batter that might be stuck. If it's too tender, let it cool a little longer. It will help prevent cracks as the cheesecake cools and shrinks.
Cool completely to room temperature in the pan on a wire rack, cover it with plastic wrap (still in the pan), and refrigerate for at least 6 to 8 hours before cutting and serving. I chill it for 1 or 2 days for the creamiest consistency before removing it from the pan.
Notes
Baking time: consider that all ovens and pans are different, even if they look similar. The baking time in my recipes is as accurate as possible, but it may take you more or less time. You can use a thermometer to check that your oven is at the right temperature. I recommend keeping track of how your oven works and noting any minor details that may need adjustment. Cheesecake bars need to be kept chilled. Don't store them at room temperature.Extra thick crust: if you like a larger ratio of crust to filling, use 1 ½ cups of crumbs and 6 tablespoons of butter.Clean-cut cheesecake dessert bars: Chill the baked cheesecake in the pan for several hours, then cut it cold. It's the easiest way to get clean squares. Wipe the knife between cuts to keep it clean each time.You can serve these bars with a homemade blueberry sauce for an extra dose of berries.