Preheat your oven to 375°F (190°C) conventional. Lightly grease an 8x8-inch baking tin and line it with a long sheet of parchment paper so it comes up the sides with a bit of overhang.

To a food processor, add all-purpose flour, cornstarch, powdered sugar, and salt. Mix for about 5 seconds to allow all the dry ingredients to combine well. Next, add in the cold unsalted butter that has been cut into small cubes and mix until the mixture resembles a sand-like consistency.

Transfer two-thirds of the mixture to the lined baking pan and spread it out evenly. Using your hands, press the crumbs into the base of the tin in an even layer. Bake for 15 minutes, or until the top is lightly browned.

While the crust is baking, in a large bowl add the chopped strawberries along with the cornstarch, lemon juice, and sugar. Mix until everything is nicely combined, then spread evenly over the warm crust.

Lightly mix the remaining dough with your hands while gently pressing to form crumbs. Sprinkle the crumbs evenly over the strawberries.

Bake for another 35 minutes, or until the top is lightly browned and the strawberries are bubbling around the edges.

Let the bars cool completely in the tin (about an hour), then place in the fridge for another hour to firm up. Remove from the fridge and run a thin knife along the edges of the pan to help release the bars, then use the parchment overhang to carefully lift them out. Slice and enjoy!