1. For the Pumpkin Spice Cookies:

2. In a medium-sized bowl, whisk together the flour, baking soda, salt, pumpkin pie spice, and cinnamon.

3. In another bowl, beat the melted butter and brown sugar (and optional granulated sugar) with a mixer until light and fluffy, about 2 minutes.

4. Add the egg (optional), vanilla extract, and pumpkin puree. Scrape down the bowl sides and mix well.

5. On low speed, slowly add the dry ingredients to the wet mixture. Mix until just combined—don’t overmix.

6. Chill the cookie dough in the fridge for 1 hour.

7. Preheat the oven to 350°F (175°C). Line baking sheets with parchment paper or silicone mats.

8. Using a large scoop (about 3 tablespoons), portion the dough and place 2 inches apart on baking sheets.

9. Flatten each dough ball gently with your palm or the bottom of a glass.

10. Bake for 12–15 minutes, or until edges are set and centers look just done.

11. Cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.

12. For the Pumpkin Spice Buttercream:

13. In a bowl, beat the butter and cream cheese until smooth.

14. Reduce mixer speed to low, and add powdered sugar one cup at a time until incorporated.

15. Add the vanilla extract, pumpkin pie spice, and heavy cream.

16. Beat on high speed for 3–5 minutes until fluffy and spreadable.

To Assemble:

Pipe or spoon buttercream onto the flat side of half the cookies.

Gently press the remaining cookies on top to sandwich together.