Move the oven racks to the upper-middle and lower-middle positions and preheat the oven to 350 degrees. Line two baking sheets with parchment paper or silicone baking mats.
In a large bowl, beat together butter and brown sugar on medium speed until smooth and creamy, about 2-3 minutes.
Add the pumpkin, eggs, and vanilla extract and beat until well combined, about 1 minute.
In a medium bowl, whisk together flour, baking powder, salt, and spices.
Gradually add the dry ingredients to the pumpkin mixture until well incorporated.
Stir in chocolate chips and walnuts.
Using a cookie scoop or a spoon, drop the dough onto the prepared baking sheets. Top the cookies with additional chocolate chips (optional).
Bake at 350 degrees F for 10-12 minutes, or until the edges of the cookies are
lightly browned.
Remove from the oven and let the cookies cool on the baking sheets for 5 minutes before transferring to cooling racks.