Prep the oven: Heat to 350°F (175°C). Line two baking sheets with parchment paper.
Mix wet ingredients: In a large bowl, whisk melted butter, brown sugar, and granulated sugar until smooth.
Whisk in egg yolk and vanilla. Stir in pumpkin puree until fully combined.
Add pudding mix: Sprinkle in the dry instant pudding mix and whisk until the batter looks thick and glossy.
Combine dry ingredients: In a separate bowl, whisk flour, baking soda, salt, cinnamon, and pumpkin pie spice.
Bring it together: Add dry ingredients to wet. Stir with a spatula just until no dry streaks remain.
Fold in chips if using. The dough will be soft.
Chill briefly (recommended): Cover and chill for 20–30 minutes to make scooping easier and help prevent spreading.
Scoop and space: Use a 1.5-tablespoon scoop and drop mounds 2 inches apart on prepared sheets. For thicker cookies, keep them mounded; for wider cookies, gently flatten the tops.
Bake: Bake 9–12 minutes, until edges look set and centers are slightly soft.
They’ll finish setting as they cool.
Cool: Let cookies rest on the sheet for 5 minutes, then move to a rack to cool completely.