Preheat oven to 350°F (180°C). Line baking sheets with parchment paper.

In the bowl of a stand mixer fitted with the paddle attachment, beat butter and brown sugar at medium speed until fluffy, 2 to 3 minutes, stopping to scrape sides of bowl. Beat in pumpkin and vanilla. Add eggs, one at a time, beating well after each addition.

In a medium bowl, whisk together flour, pumpkin spice, baking soda, baking powder, and salt. With mixer on low speed, gradually add flour mixture to butter mixture, beating until combined. Using a scant ¼-cup spring-loaded scoop, scoop batter, and drop 2 inches apart on prepared pans. Using damp fingers, pat batter to flatten tops, creating 2½-inch rounds.

Bake until a wooden pick inserted in center comes out clean, 13 to 15 minutes. Let cool on pans for 5 minutes. Remove from pans, and let cool completely on wire racks.

Place Mascarpone Filling in a piping bag fitted with a large round tip (Wilton #12). Pipe Mascarpone Filling onto flat side of half of cookies. Place remaining cookies, flat side down, on top of filling. Refrigerate in an airtight container for up to 3 days.