Preheat oven to 350 degrees. Spray or line baking sheets with parchment paper.
Mix together the following ingredients until well combined: salt, baking powder, baking soda, flour, clove, ginger, cinnamon, and nutmeg.
In a separate bowl, mix together brown sugar and oil until uniform, then add pumpkin puree, eggs, vanilla extract, and mix.
Add flour mixture to pumpkin mixture, adding a little flour at a time, until uniform.
Scoop mixture with an ice cream scoop with a release mechanism, and place 1 inch apart on baking sheets. Bake for 20 minutes. Insert a toothpickinto pie; it should come out clean, otherwise continue to bake until done.
Make cream-cheese frosting: Put powdered sugar in large bowl, and set aside. In your mixer, beat room-temperature butter until smooth (make sure there are no lumps), then add cream cheese, maple syrup, and bourbon, and beat until uniform. Add powdered sugar a little at a time, and beat until mixed to a smooth consistency.
Transfer frosting into a piping bag and cut a medium-sized hole on the end. Once cakes have cooled, add a large dollop of frosting, working in a circular motion, to each cake. Top, and push down gently to fill out center of each whoopie pie. Refrigerate for 3o minutes to an hour, and serve.
Tip: Let cakes cool slightly and serve while still warm. Nothing beats warm cookies straight from the oven!