Firstly, mill the flour. You can weigh and mill all the flour at once, or divide it and mill separately. I went ahead and milled the flour for just the crust first so I could get that going, since I needed to par bake that first.

Preheat the oven to 350*F, and prepare a 9x13 baking pan with parchment paper, or baking spray.

To the flour for the crust, add powdered sugar, salt, and cubed cold butter. You can use a mixer, your hands, or a pastry cutter to cut the butter into the flour/powdered sugar mixture. Mix until there are about pea-sized crumbles of butter. It will still seem sandy at this time.

Press this mixture into your prepared 9x13 pan. The butter will melt as it cooks making it all cohesive.

Bake this for 15-18 minutes. Set aside to cool while you make the next layer (the filling.)

To make the filling, add softened cream cheese and sugar to a large bowl, or stand mixer. Beat on medium until smooth, scraping down sides as needed.

Once the mixture is creamy and smooth, then add the sour cream (or yogurt) and vanilla. Mix to incorporate.

Then, add eggs one at a time, mixing between each egg to incorporate. Scrape sides as needed.

Add lemon zest and lemon juice to mixture, and mix until incorporated.

After the crust has cooled a bit (15 - 20 mins), then you can pour the filling over the crust.

Evenly sprinkle the washed & dried fresh blueberries over the filling mixture. They will sink into the filling a bit, that is fine.

Preheat oven again to 350* F while you prepare the crumble topping.

To make the crumble topping, add fresh milled flour, salt, and powdered sugar to a medium bowl, and whisk until incorporated.

Pour the melted butter in while stirring, and then add lemon zest. Stir until incorporated. It should be a bit crumbly. If not you may need to add a bit more flour.

Sprinkle the crumble topping evenly over the filling and blueberry mixture.

Bake the whole dessert for 50-55 minutes until the filling is slightly firm, without being jiggly in the center. If using a glass baking pan, make sure the bottom of the crust is baked, and lightly golden brown.

After baking, let the whole dessert cool for about 30-40 minutes on the counter. Then, place it in the fridge for at least 2 hours to finish chilling. The flavors in this dessert only get better as it sits in the fridge. If you can make this a day ahead, even better!

If you are using the optional lemon glaze, make it just before serving the dessert bars.

To make the lemon glaze, add powdered sugar, milk, lemon juice, and vanilla extract to a small bowl, and whisk until combined. You are looking for a drizzle consistency off your spoon. If it is too thick, add more milk. (Just use a tiny bit at a time, because a little goes a long way!) If too thin, add more powdered sugar.

Drizzle the lemon glaze before serving, serve. You can add a bit more lemon glaze to each piece if desired.

Enjoy!