BROWNIES: In a small bowl, beat together the eggs and vanilla; set aside.
In a large bowl, stir together melted butter, granulated sugar, cocoa powder and salt, until well combined. Whisk in egg and vanilla mixture. Add flour, stirring until well combined.
Pour the brownie batter into a parchment lined 8 x 8-inch baking dish. Bake for 25-30 minutes. Cool for 20-30 minutes.
PECAN PIE TOPPING: Meanwhile, in a large mixing bowl, using a hand mixer, beat together corn syrup and brown sugar until smooth. Add the eggs, vanilla and cinnamon, beat until combined. Add melted butter and bourbon if using, beat until well combined. Stir in pecans.
Pour the pecan pie mixture over the cooled brownie layer. Bake for an additional 25 to 30 minutes, until the center is set. Let cool completely.
Score into 16 bars then refrigerate for at least two hours before serving. Remove from the pan and carefully cut into 16 squares. Refrigerate leftovers.