In a medium sauce pot, melt butter over medium heat. Bring the butter to a boil, lower heat and continue cooking until butter is a deep golden brown, about 10 minutes. Stir the butter frequently to avoid burning. Allow butter to cool for 20 minutes.
Preheat oven to 350° Grease a 9×13-inch baking dish.
In a bowl, whisk together the flour, pumpkin pie spice, salt and baking powder.
In a large mixing bowl, combine the cooled butter and brown sugar. Mix in the pumpkin, egg and vanilla.
Pour the dry ingredients into the wet ingredients and mix until all dry ingredients are moistened. Fold in the white baking chips and nuts.
Spread the blondie batter evenly into the prepared pan and bake for 35 minutes. Allow the Pumpkin Blondies to cool completely before slicing.