Preheat the oven to 350F (180C) and line cookie sheets with parchment paper.
Using paper towels or a clean dish cloth, squeeze and blot the pumpkin puree to remove excess moisture from the pumpkin. Set aside.
In a medium bowl, whisk together the flour, cinnamon, ginger, nutmeg, cloves baking soda and salt. Set aside.
In a large bowl, beat together the butter, brown sugar and granulated sugar until creamed (you should no longer see lumps of brown sugar or butter - sugar granules is OK and expected).
Add the blotted pumpkin puree, vanilla extract, molasses (or honey), and egg yolk to the butter mixture. Beat together until combined.
Mix the flour mixture into the butter mixture, starting with the mixer on a low speed.
Stir in the oats until evenly mixed into the dough.
Scoop the cookie dough into balls so that each cookie is about 1 to 1.5 tablespoons of dough. I use a cookie scoop for this. Place cookie dough balls about 2 inches (5 cm) apart on the lined cookie sheets.
Bake 1 sheet at a time in the middle of the preheated oven. They'll bake for about 7-10 minutes, or until the tops look set.
Cool the cookies on the cookie sheets for at least 10 minutes before transferring to a cooling rack to continue cooling.