Preheat the oven to 350 degrees F
In a large bowl, beat together the butter (softened and not melted) with the brown sugar and white sugar
Beat in the pumpkin, egg yolk, and vanilla
In another bowl stir together the flour, quick oats, cinnamon, baking soda, baking powder, pumpkin pie spice and salt
Add the dry to the wet and mix until just combined
Cover and place in the fridge for at least 30 minutes and preferably 1 hour. This is a crucial step and if skipped your cookies will likely spread like a pancake
Once the dough has been chilled, line a baking mat with a nonstick liner (or parchment paper)
Once you’ve rolled about 6-8 balls of dough, chill on the cookie sheet in the fridge for another 10-15 minutes
Bake for 12-14 minutes or until very lightly browned at the bottom/sides. The key to these cookies is slightly under-baking – that will keep them soft and chewy in the inside