In a large mixing bowl, melt unsalted butter, then add light brown sugar and pumpkin puree. Stir until smooth.

Incorporate egg yolk and vanilla extract into the wet mixture. Mix until glossy and cohesive.

In a separate bowl, whisk together flour, baking soda, baking powder, salt, cinnamon, and nutmeg. Gradually add to wet mixture, folding gently.

Fold in chocolate chips using a spatula until evenly distributed.

Cover with plastic wrap and refrigerate the dough for at least 30 minutes.

Preheat oven to 350°F (180°C) and line a baking sheet with parchment paper.

Scoop tablespoons of dough onto the prepared baking sheet, spacing them 2 inches apart. Bake for 9-10 minutes.

Let cookies cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.