Preheat your oven to 350°F and line a 9x13-inch pan with parchment paper. In a large bowl, whisk together flour, powdered sugar, and salt. Cut in cold butter using a pastry cutter or your fingers until the mixture resembles coarse crumbs with some pea-sized butter pieces. Press the mixture firmly into your prepared pan using the bottom of a measuring cup for even distribution.

Bake the shortbread base for 18-20 minutes until the edges are lightly golden and the center looks set but not browned. Remove from oven but keep the temperature at 350°F.

While the crust bakes, whisk together eggs and brown sugar in a large bowl until smooth and slightly lightened. Stir in corn syrup, melted butter, and vanilla extract until completely combined. Fold in chopped pecans and chocolate chips, ensuring even distribution.

Pour the pecan-chocolate mixture over the warm shortbread base, spreading gently to reach all corners. Sprinkle flaky sea salt evenly across the surface. Bake for 22-25 minutes until the filling is set around the edges but still slightly jiggly in the center.

Let the bars cool completely in the pan for at least 2 hours. Use the parchment paper to lift the entire slab onto a cutting board, then cut into squares with a sharp knife, wiping the blade between cuts for clean edges.