Gingerbread Whoopie Pies

Preheat the oven to 350°F and line a baking sheet with parchment paper; set aside.
Whisk together the flour, spices, baking powder, baking soda, and salt in a large bowl; set aside.
In a separate large bowl or stand mixer fitted with a paddle attachment, cream together the butter and brown sugar on medium-high speed until light and fluffy, about 3 minutes, scraping down the sides of the bowl as needed.
Add eggs one at a time, beating until smooth after each addition, then mix in the molasses and vanilla extract.
Add half of the dry ingredients to the wet ingredients and mix on low until incorporated. Add the buttermilk and continue to mix until mostly smooth, scraping down bowl as needed. Add the remaining flour mixture and mix until just combined.
Use a medium cookie scoop, drop six 3-tablespoon (2 scoops worth) portions of batter onto the prepared baking sheet, spacing scoops 2 inches apart. Bake until cakes are puffed and tops spring back when touched, about 11 to 14 minutes. Cool for 1 minute on the baking sheet, then carefully transfer to a wire rack to cool completely, about 20 minutes. Repeat with the remaining batter.
Prepare the frosting according to the recipe directions.
To assemble whoopie pies, pipe filling over flat sides of 12 cakes. Top with remaining 12 cakes, flat side down, and press gently to adhere. Serve immediately or wrap individually in plastic wrap and store at room temperature for up to two days.