Preheat oven to 375℉
Spray and 8x8 inch baking pan with cooking spray. Line the bottom of the pan with parchment paper, leaving overhang on two sides.
Whisk together the flour, pumpkin pie spice, salt and baking powder in a small mixing bowl. Set aside.
In a medium, microwave-safe mixing bowl, microwave the butter for 30 seconds. Remove bowl from microwave and stir the butter. Continue to microwave at 10 second intervals until melted, stirring between each interval.
Stir in the granulated sugar and brown sugar until combined.
Add the egg, sourdough discard, pumpkin puree, and vanilla extract and stir until smooth.
Slowly, mix in the dry ingredients until mostly smooth with no large chunks of flour present. Small, flour clumps are fine. Stir in the chocolate chips and pecans.
Pour the batter into the prepared baking pan. Use a rubber spatula to spread the batter evenly in the pan and smooth the top.
Top with reserved chocolate chips and chopped pecans.
Bake in preheated oven for 35-37 minutes, or until a toothpick inserted comes out clean.
Allow to cool 15 minutes before serving.