Preheat your oven to 400 degrees. Line your cookie sheet with parchment paper and set aside.
Take your large pan and melt butter on low heat until the milk solids from the butter are toasted. Immediately remove from the heat and add to your stand mixer.
To bring the brown butter back to room temp. Place the stand mixer bowl into another large bowl filled with ice water. Once the butter is no longer hot to the touch, it's ready to be mixed.
Mix the brown and granulated sugar with the butter in your stand mixer on a low setting. Slowly add the sourdough discard, egg, and vanilla extract while the mixer is on low.
In a large bowl, whisk together flour, baking soda, salt, and spices.
Slowly add the dry ingredients to the wet ingredients until the dough forms.
Take your cookie scoop or ice cream scoop and add the dough balls to your cookie sheet.
Bake the sourdough discard pumpkin spice cookies at 400 degrees for 12 minutes or until golden brown.
Let the cookies cool while you make the cream cheese frosting.
After you make the cream cheese frosting and the cookies have cooled, place the frosting into a ziploc bag and cut a hole in one of the corners of the bag. This will create a piping bag to make frosting the cookies easier. If you don't have ziploc bags, adding a dollop of frosting with a spoon should also work.
Add the frosting to the center of the cookie and take an offset spatula or the back of a spoon and spread the frosting to the edges of the cookies.
Finish with adding pumpkin pie spice to the top and enjoy!