01 - Preheat oven to 350°F. Line an 8x8-inch baking pan with parchment paper, ensuring an overhang for easy lifting.
02 - In a large bowl, whisk together melted butter, packed light brown sugar, and pure maple syrup until the mixture is smooth.
03 - Add egg, pumpkin purée, bourbon, and vanilla extract to the bowl and whisk until fully combined.
04 - In a separate bowl, whisk together all-purpose flour, ground cinnamon, ginger, nutmeg, cloves, baking powder, and salt until evenly blended.
05 - Add the dry mixture to the wet ingredients. Stir gently until just incorporated; do not overmix.
06 - Gently fold in the chopped toasted pecans and white chocolate chips if using.
07 - Spread the batter evenly in the prepared pan. Bake for 32 to 35 minutes, until edges are set and a toothpick inserted into the center emerges with a few moist crumbs.
08 - Allow bars to cool completely in the pan before removing using the parchment overhang. Cut into 16 even squares.