Preheat your oven to 350°F. Line two baking sheets with parchment paper and set them aside.
In the bowl of a stand mixer, beat together the granulated sugar, brown sugar, and oil until the mixture is well blended.
Add the pumpkin puree, eggs, and vanilla extract, mixing until everything is smooth and combined.
Gradually stir in the flour, salt, baking soda, baking powder, and pumpkin pie spice. Mix until everything is just blended. Scrape down the sides of the bowl as needed, but be careful not to overmix the dough.
Using a cookie or ice cream scoop, drop dollops of the batter on the prepared baking sheets, spacing them out slightly.
Bake for 10-12 minutes, or until the centers are set and no longer look wet. Let the cookies cool completely on the baking sheets before handling.
While the cookies cool, prepare the cream cheese filling. In a stand mixer fitted with the paddle attachment, beat the softened butter until smooth.
Add the cream cheese and continue mixing until silky and lump-free.
Add the powdered sugar and vanilla, and mix on low until combined. Then increase the speed to medium and mix until the frosting becomes fluffy and light, scraping down the bowl as needed.
Spoon the frosting into a piping bag and set it aside until you're ready to assemble.
Once your cookies are fully cooled, pair them up by size to create sandwich tops and bottoms.
Snip the tip off your piping bag and pipe a generous swirl of filling onto the flat side of half the cookies.
Gently press the remaining cookies on top to create soft, delicious pumpkin whoopie pies.