Preheat the oven to 350 degrees F. Line an 8 by 8 metal pan with parchment paper.
To a medium-sized bowl, whisk together the canned pumpkin, sourdough discard, coconut oil, brown sugar, granulated sugar, egg and vanilla extract until fully incorporated and smooth.
To a small bowl whisk together the flour, baking powder, baking soda, spices and salt.
Add the dry ingredients on top of the wet ingredients and mix together until no dry streaks remain. Pour the mixture into the parchment-lined baking pan.
Bake for about 20-25 minutes until baked through. Insert a toothpick or sharp knife into the center of the bars. If it comes out clean, it's finished baking. If not, let it bake a few more minutes and check again.
Whip up the frosting while the bars cool. Whip together the softened cream cheese, butter, powdered sugar, vanilla extract and salt until smooth and creamy. Add a splash of cream if needed to smooth out the consistency.
Spread the frosting on top of the cooled bars. Enjoy!
