In a mixing bowl, stir together flour, granulated sugar, baking powder, and cinnamon. Cut in the ½ cup cold butter with a pastry blender until mixture resembles coarse crumbs. Stir in pecans. Press mixture evenly into the bottom of an ungreased 13-by-9-by-2-inch baking pan. Bake for 10 minutes.
Meanwhile, in a small saucepan combine the ¼ cup butter and square of semisweet chocolate; heat and stir over low heat until melted; set aside.
In bowl of electric mixer, beat eggs. Add brown sugar, bourbon, and vanilla. Add melted butter and chocolate and blend well. Pour over crust. Return to oven and bake another 20 minutes or until set. Cool on wire rack before cutting into bars.
Recipe by The Culinary Cellar at https://theculinarycellar.com/chocolate-pecan-pie-bars/