Start by draining the excess moisture from the pumpkin puree by wrapping it in a paper towel or cheesecloth and gently squeeze over a small bowl for no more than 5 minutes. Be gentle to avoid tearing the towels, and aim for a paste-like consistency.
In a large mixing bowl, combine butter, sugars, and pumpkin puree.
Then add vanilla extract and egg yolk. Mix until smooth using a hand mixer on low speed for about 15-20 seconds.
Incorporate all dry ingredients into the mixture – except for the chocolate chips. Blend until no flour is visible.
Carefully fold in the chocolate chips using a silicone spatula. Avoid overmixing.
Cover the dough with a lid or aluminum foil and chill for 15 minutes.
Preheat the oven to 350°F and prepare two baking sheets with parchment paper to prevent sticking.
Use a medium cookie scoop to portion dough balls onto the baking sheets, spacing them about 2 inches apart.
Bake for 12 minutes, or until the bottom edges turn golden brown and set.
Remove from the oven promptly, allowing the cookies to rest on the baking sheet for 5 minutes before transferring them to a wire cooling rack.