To toast the pecans, spread the nuts in a single layer on a large rimmed baking sheet lined. Bake in a preheated 350 degree F oven until slightly darkened, about 8 to 12 minutes. Stir the pecans halfway through to prevent burning. Set aside.
In a large mixing bowl, whisk together the brown sugar, syrup, melted butter, vanilla, salt and bourbon until smooth. Add the toasted pecans and fold together using a spatula until all nuts are evenly coated. Spoon the topping over the crust and chocolate chips. Gently spread the topping into the corners of the pan but don’t worry if there are bare patches. The topping will spread a little as it bakes. Bake for 25 to 30 minutes or until the topping is bubbling across the entire surface. Remove from the oven and top with the remaining chocolate chips.
Cool completely in the pan, then sprinkle with the sea salt, if using. Using the parchment overhang, remove the bars from the pan and transfer to a cutting board. Cut into 24 bars.