Preheat oven to 350° and place baking rack in middle of oven. Lightly grease 9 inch square pan. Cut two pieces of parchment paper 9 inches wide and long enough to press in pan and have excess over sides. Line pan with the two piece of parchment paper by first pressing one into bottom of pan and up sides (you want hang over for handles). Lay the second piece the opposite way so you have hangover on the other two sides. This is so you can lift bars out easily. Lightly grease bottom and sides of paper. (See example of parchment paper placement in the last post picture)

Place flour, brown sugar, pecans, salt, and baking powder in food processor. Process mixture until it resembles coarse cornmeal, about five 1-second pulses. Add butter and pulse until mixture resembles sand, about eight 1-second pulses.

Press mixture evenly into prepared pan and bake until crust is light brown and springs back when touched, about 20 minutes.

While crust bakes, whisk together brown sugar, melted butter, corn syrup, bourbon (optional), vanilla, and salt in medium bowl until just combined.

Add egg and whisk until incorporated.

Pour filling on top of hot crust and sprinkle pecans evenly over top.

Bake until top is brown and cracks start to form across surface, 22 to 25 minutes.

Cool on wire rack for 1 hour. Remove bars from pan parchment handles and transfer to cutting board. Cut into bars that measure 1 1/2 inches by 2 1/4 inches.