Preheat the oven to 350?F and grease a 9x13-inch baking pan with butter and flour.

Melt the butter in a small saucepan over medium heat until it starts to bubble and the milk solids turn golden. Remove from heat and let cool slightly.

In a medium mixing bowl, combine the flour, pumpkin pie spice, baking soda, and salt. Whisk to combine.

Pour the cooled butter into a large mixing bowl. Add the brown sugar, egg, pumpkin pur?e, and vanilla extract. Whisk until smooth.

Fold the dry ingredients into the wet ingredients until just incorporated. Add the white chocolate chips and chopped pecans, stirring to distribute evenly.

Transfer the batter to the prepared baking pan and spread evenly. Bake for 35 minutes or until a toothpick inserted into the center comes out with a few moist crumbs.

Allow to cool completely in the pan. Slice into squares and serve.