Preheat oven to 350°F (177°C). Line two large baking sheets with parchment paper or silicone baking mats and set aside.
In the bowl of a stand mixer fitted with the paddle attachment, or in a large mixing bowl using a handheld mixer, mix the butter, granulated sugar, and brown sugar together until fully combined. Mix in the pumpkin puree, egg yolk, and vanilla extract until well combined, stopping to scrape down the sides of the bowl as needed.
In a separate bowl, whisk together the flour, pumpkin pie spice, ground cinnamon, baking soda, and salt. Add the dry ingredients to the wet ingredients and mix until just combined. Mix in the chocolate chips on low speed (or fold them into the cookie dough) until fully combined.
Using a 1.5 tablespoon cookie scoop, scoop balls of the cookie dough onto the prepared baking sheets, making sure to leave a little room between each one. Slightly flatten each ball of cookie dough.
Bake at 350°F (177°C) for 11-13 minutes or until the tops of the cookies are set. Remove from the oven and cool on the baking sheet for 10 minutes, then transfer to a wire rack to cool completely.
Notes
Storage instructions: Store cookies in an airtight container in the refrigerator for up to 5 days.Freezing instructions: Once the cookies have cooled, you may freeze the baked cookies for up to 3 months. Thaw to room temperature before serving. Cookie dough will also freeze well for up to 3 months, thaw overnight in the refrigerator.Pumpkin puree: Make sure to use pumpkin puree and not pumpkin pie filling. The only ingredient in pumpkin puree will be pumpkin.Egg Yolk: It's best to use a room temperature egg yolk in this recipe. If you forget to set the egg out ahead of time, just place it in a bowl of warm water for 5-10 minutes before separating it. Chocolate Chips: The chocolate chips are completely optional! Feel free to replace them with white chocolate chips or even 1/2 - 3/4 cup of your favorite chopped nuts.