Preheat oven to 350 degrees and line your baking sheets with parchment paper.
Combine the dry ingredients: flour, baking powder, baking soda, salt, and spices in a bowl.
In a separate bowl, combine the sugar, vegetable oil, egg, pumpkin, and vanilla.
Add the dry ingredients to the wet ingredients, mixing to thoroughly combine.
Using a medium-size ice cream or cookie scoop, place the batter on the prepared baking sheets. Space the scoops of batter 1-2 inches apart.
Bake for 10-12 minutes, or until the cookies/cake discs are set.
Place on a cooling rack.
While the cookie parts of the whoopie pie cool, make the filling by beating together the shortening, cream cheese, and marshmallow fluff, and 1 tbsp of milk.
Gradually add the powdered sugar until the desired consistency. Add the other tbsp of milk if the consistency needs it.
Place filling in a piping bag so that you can easily put the filling on the bottom of half of the cookies. Top with the other half of the cookies so that it looks like a sandwich.
Place the pies in the refrigerator for about an hour so that the filling and cookies can set up.
