Preheat oven to 350°. Line a 9x13" baking pan with parchment paper, leaving some paper to hang over the sides to use as a handle for lifting the bars out of the pan later. (Always thinkin' ahead!)
In a food processor (or with an electric mixer) mix together flour, cocoa powder, butter, sugar, and salt until fully combined and crumbly. Press evenly and firmly into the bottom of the pan and bake for 15 minutes. Set aside.
In a medium saucepan over medium-high heat, bring brown sugar, butter, salt, and cream to a boil, stirring continuously until sugar dissolves. Boil for two minutes stirring occasionally. Remove from heat. Stir in 1 ½ cups of chopped pecans.
Pour the caramel and pecans over the baked shortbread. Bake at 350° until caramel bubbles and darkens in color, about 18-20 minutes.
While the bars are baking, place chocolate chips, or chopped chocolate in a heat safe bowl with the heavy cream. Set the bowl over a pot of barely simmering water and stir until the chocolate is melted and everything is combined and smooth. You made ganache!
Spread the ganache evenly over the caramel and pecan layer and sprinkle with the remaining ½ cup of pecans. Finish with flaky sea salt if desired. Allow to cool completely before slicing.
Cut into slices using a warm dry knife, wiping between slices. I do this by dipping the knife in a tall glass filled with hot water and drying it on a towel then slicing. Slice, dip, dry, repeat, EAT!