Preheat your oven to 350°F (175°C). In a medium bowl, combine 1 cup of all-purpose flour, 1/4 cup granulated sugar, and 1/4 teaspoon salt. Add the softened 1/2 cup unsalted butter and mix until the dough resembles coarse crumbs. Press this mixture evenly into the bottom of your greased 8x8-inch baking pan to form the crust. Bake for 15 minutes until it’s lightly golden and firm to the touch.
While the crust bakes, whisk together 1/2 cup packed brown sugar, 1/2 cup corn syrup, 2 large eggs, and 1 teaspoon vanilla extract in a separate bowl until smooth. Stir in the chopped 1 cup pecans to evenly distribute the nuts throughout the filling.
Once the crust is out of the oven, pour the pecan filling evenly over the hot crust. Return the pan to the oven and bake for another 25-30 minutes or until the filling is set and slightly puffed. The bars should be golden brown and firm around the edges but still slightly soft in the center.
Allow the bars to cool completely in the pan on a wire rack. This cooling step is crucial for the filling to set properly. Once cooled, use a sharp knife to cut into squares or rectangles. For clean edges, wipe the knife with a warm, damp cloth between cuts.