In a medium bowl, melt the butter, over medium heat. Swirl it around ever once in a while to make sure that it is melting evenly. The butter will eventually begin to foam and turn a bright yellow, then begin to turn brown. Once it has started to brown and smells nutty, pour it into a medium bowl. If you have burned bits on the bottom, pour it through a strainer.
In a large bowl, combine the whole wheat pastry flour, cornstarch, salt, baking powder and pumpkin pie spice. Set aside.
Stir the brown and white sugar into the browned butter, until no brown sugar lumps are left. (since the butter is melted, you don't need to use an electric mixer)
Whisk the egg, vanilla extract and pumpkin puree into the butter mixture until well combined.
Stir the wet ingredients into the dry ingredients to form a dough. Your dough will be very soft and sticky. Then, stir in the butterscotch chips.
Chill in the refrigerator for 30 minutes
Once the cookies have chilled, preheat your oven to 350 degrees F, and line a cookie sheet with parchment paper.
Drop the cookies into 1 1/2 sized balls (I use a cookie scoop) and flatten to about 1/2 inch thick.
Bake for 12-13 minutes. You will think the cookies are under done, but they continue baking on the pan.
Let them cool completely on the pan