In a medium saucepan, melt butter over medium-low heat. Remove from heat and stir in brown sugar and sugar. Stir for 2-3 minutes or until it becomes silky smooth and glossy. Let cool for 5-10 minutes.

Stir in vanilla and egg yolk. After it is completely mixed, stir in pumpkin puree.

Add flour, oats, baking soda, salt, cinnamon, and pumpkin pie spice.  Stir well to incorporate ingredients.

Let chill for 15 minutes. Preheat oven to 350 degrees. Stir in white chocolate chips.

Using a cookie scoop or two spoons, drop cookie dough on baking sheets, lined with parchment paper or Silpat. Bake for 10-13 minutes or until lightly golden brown on edges. Let set up for 5-10 minutes before removing from pan.