• Preheat the oven to 350°F and grease and line an 8x8-inch pan with parchment paper.

Crust

• In the bowl of a stand mixer fitted with the paddle attachment (or with a hand mixer), beat the butter for a couple of minutes until light and fluffy, then scrape down the sides.
  ½ cup unsalted butter
• Add in the sugar and vanilla and mix until combined, then add in the flour and salt and mix until a clump of dough forms.
  ¼ cup light brown sugar, 2 teaspoons vanilla extract, 1¼ cups all-purpose flour, ½ teaspoon kosher salt
• Press the dough into the prepared pan (get it the whole way to the corners and edges) and bake for 15 minutes.

Filling

• While the shortbread is baking, mix together the brown sugar and cocoa powder to get rid of any cocoa clumps.
  ¾ cup light brown sugar, 2 tablespoons cocoa powder
• Mix in the eggs, butter, heavy cream, corn syrup, salt, vanilla, and melted chocolate until a smooth mixture forms.
  2 large eggs, 2 tablespoons unsalted butter, ¼ cup heavy whipping cream, ¾ cup light corn syrup, ½ teaspoon kosher salt, 1 tablespoon vanilla extract, 4 oz semi-sweet chocolate

Assembly

• Remove the crust from the oven and top evenly with almost all of the pecans. Pour over the chocolate mixture and spread evenly.
  2 cups chopped pecans
• Sprinkle with the remaining pecans.
• Return to the oven and bake for 30-35 minutes until set around the edges and has a slight jiggle in the center (but not sloshy). Gently place a piece of foil on top to prevent too much browning, if needed.
• Cool at room temperature, then refrigerate for 2-3 hours before cutting and serving.