Prep Pan & Oven: Preheat your oven to 350°F (175°C). Line a 9x13-inch metal baking pan with parchment paper, leaving an overhang on the sides for effortless removal later.

Bake Shortbread Crust: In a medium bowl, whisk together flour, granulated sugar, and sea salt. Pour in melted butter and vanilla extract, stirring with a fork until a soft, crumbly dough forms. Press dough evenly into the bottom of the prepared pan. Bake for 18 to 20 minutes until the edges are lightly golden. Remove from oven and let rest while making filling.

Brown the Butter: In a light-colored saucepan over medium heat, melt 1/2 cup butter. Swirl occasionally as it foams and sizzles. After 4 to 5 minutes, golden brown specks will form on the bottom with a heavenly nutty aroma. Immediately pour brown butter into a heatproof bowl to stop the cooking.

Whisk Pecan Caramel Filling: Whisk the warm brown butter, dark brown sugar, maple syrup, heavy cream, eggs, 1 tbsp flour, vanilla extract, and kosher salt together until completely glossy and emulsified. Fold in the toasted chopped pecans.

Pour & Bake: Pour the glossy pecan mixture over the warm pre-baked shortbread crust, spreading the pecans evenly to the corners with a spatula. Return to the oven and bake at 350°F (175°C) for 22 to 25 minutes, until the center is set with a gentle, slight jiggle.

Cool, Slice & Garnish: Remove from oven and immediately sprinkle with flaky sea salt. Allow bars to cool completely to room temperature in the pan, then chill in the refrigerator for at least 1 hour for clean, razor-sharp bakery slices. Lift out using the parchment handles, slice into 16 squares, and serve!