In a large mixing bowl, whisk together the all-purpose flour, powdered sugar, and fine sea salt until well combined. Next, rub in the cold, cubed unsalted butter with your fingertips until the mixture resembles coarse crumbs. Gently fold in the toasted pecan halves.

Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking dish and firmly press the dough into the pan, ensuring an even thickness of about ½ inch. Bake for 20-25 minutes, until the edges are light golden brown.

While the shortbread base is baking, combine the heavy cream, light brown sugar, unsalted butter, pure vanilla extract, and a pinch of sea salt in a medium saucepan. Heat over medium heat, stirring continuously, until the mixture comes to a simmer and thickens slightly, about 2-3 minutes.

Once the shortbread base is finished baking, let it cool in the pan for about 10 minutes. Drizzle the warm caramel glaze over the cooled shortbread, ensuring it's spread evenly to the edges.