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 easy lifting later.

In a medium bowl, whisk together the melted unsalted butter, granulated sugar, light brown sugar, pure vanilla extract, and fine sea salt until well combined. Stir in the all-purpose flour until a soft, crumbly dough forms.

Press the dough firmly and evenly into the bottom of the prepared pan using the flat bottom of a measuring cup. Bake for 16 to 18 minutes until the edges are light golden brown. Remove from the oven and set aside while making the filling.

In a heavy-bottomed medium saucepan, combine the 1/2 cup cubed unsalted butter, dark brown sugar, and pure maple syrup. Cook over medium heat, stirring frequently, until the butter melts and the sugar dissolves.

Bring the mixture to a gentle boil and let it bubble for 2 to 3 minutes without stirring, creating a rich caramelized base. Remove from heat and carefully whisk in the heavy cream and vanilla extract (it will bubble up vigorously).

Fold in the chopped pecans and whole pecan halves until thoroughly coated in the molten maple caramel.

Immediately pour the warm pecan caramel filling over the warm par-baked shortbread crust, spreading it into an even layer with an offset spatula.

Return the pan to the oven and bake for 18 to 20 minutes until the filling is bubbling across the entire surface. Remove from the oven and immediately sprinkle generously with flaky Maldon sea salt.

Allow the bars to cool completely in the pan at room temperature for at least 2 hours (or chill for 1 hour) so the caramel sets firmly. Use the parchment overhang to lift the slab onto a cutting board and slice into 16 clean squares with a sharp chef’s knife.