• Preheat oven to 350 F and line a baking sheet with parchment paper.
• In a medium bowl, combine flour, pumpkin pie spice, baking soda and salt.
• In the bowl of an electric mixer fitted with the paddle attachment, beat butter and sugar on medium-high until light and fluffy, about 2-3 minutes.
• Beat in egg until well combined.
• With the mixer on low speed, add molasses, buttermilk and dry ingredients alternately in 3 parts, beginning and ending with the dry ingredients, beating just until incorporated.
• Drop tablespoons of batter onto the prepared baking sheet.
• Place into the oven and bake until the edges are golden brown but the center is still moist, about 10-12 minutes.
• Remove from the oven and cool completely on a wire rack before frosting.

Filling

• Using a standing mixer, beat together all ingredients until combined and stiff with peaks.
• Scoop into the piping bag.
• Match up the cookies to their size partners.
• Pipe a dollop of frosting onto the bottom cookie. Place the top cookie on top of the frosting and lightly press the cookies together. Plate and serve!