Preheat oven to 350°F (175°C). Line a 9x9-inch or 9x13-inch square metal baking pan with parchment paper, leaving an overhang on the sides for easy lifting.

In a mixing bowl, beat softened European butter and powdered sugar together until creamy and smooth. Stir in vanilla and sea salt, then gradually add flour until a soft, crumbly dough forms.

Press the shortbread dough evenly into the bottom of the prepared pan with your fingers or the flat bottom of a measuring cup. Bake for 18 to 20 minutes until the edges are pale golden and set. Remove and let cool slightly while preparing filling.

In a medium bowl, whisk together melted butter, packed dark brown sugar, pure maple syrup, beaten eggs, heavy cream, vanilla extract, cinnamon, and fine sea salt until glossy and emulsified.

Stir the chopped pecans into the caramel mixture. Pour the warm pecan filling evenly over the pre-baked shortbread crust, spreading to the edges. Arrange extra whole pecan halves across the top for bakery-style visual presentation.

Bake at 350°F (175°C) for 24 to 28 minutes until the center is set and edges are bubbling gently (it should have a slight jiggle in the very center like pumpkin pie, but not liquid).

Remove from oven and sprinkle immediately with flaky sea salt. Allow bars to cool completely at room temperature for 1 hour, then chill in the refrigerator for at least 1 hour for clean, razor-sharp bakery slicing.

Use the parchment overhang to lift the entire slab onto a cutting board. Slice into 16 squares with a warm, sharp chef knife, wiping the blade clean between cuts. Serve and enjoy!