Preheat your oven to 350°F (175°C). Line a 9x13 inch baking pan with parchment paper, leaving an overhang on the sides for easy removal later. Lightly grease the parchment paper.

In a large mixing bowl, whisk together the all-purpose flour, powdered sugar, and 1/2 tsp salt.

Add the cold, diced butter to the dry ingredients. Use a pastry blender, your fingertips, or an electric mixer on low speed to cut the butter into the flour mixture until it resembles coarse crumbs and forms a dough when pressed together.

Press the dough evenly into the bottom of the prepared baking pan. Bake for 15-20 minutes, or until the edges are lightly golden. Remove from the oven and set aside while you prepare the filling.

In a medium saucepan, melt 1/2 cup butter over medium heat. Continue cooking, stirring occasionally, until the butter turns a rich golden-brown color and smells nutty. Be careful not to burn it. Remove from heat and let cool slightly for about 5 minutes.

In a large bowl, whisk together the brown sugar, corn syrup, eggs, vanilla extract, and 1/4 tsp salt until well combined.

Gradually whisk the slightly cooled brown butter into the egg mixture until smooth.

Stir in the pecan halves until they are evenly coated in the filling.

Pour the pecan filling evenly over the pre-baked shortbread crust.

Return the pan to the oven and bake for 30-35 minutes, or until the filling is set and the edges are lightly browned. A slight jiggle in the center is normal.

Remove from the oven and let cool completely in the pan on a wire rack for at least 2-3 hours, or ideally, chill in the refrigerator for 1-2 hours for cleaner slices.

Once completely cooled, use the parchment paper overhang to lift the bars out of the pan. Place on a cutting board and cut into 24 squares or bars using a sharp knife.