To make brown butter melt 2 sticks of butter over medium heat in a pot or medium saucepan, then bring to a boil. Once butter melts and starts boiling, swirl the pan constantly until the butter becomes somewhat foamy and becomes amber brown color. You should see little golden brown bits on the bottom of the pan and have a nutty aroma. Remove from heat and pour into a separate small bowl allowing the butter to cool and stop cooking. Cool for 20-30 minutes in the refrigerator.
Place the pumpkin puree in a small bowl and blot it down with several paper towels to remove excess moisture. You will be surprised how much water gets absorbed! Measure out 1/2 cup of pumpkin puree and set aside.
In a large bowl, whisk together the cooled browned butter, sugars and vanilla until smooth. Add in the pumpkin puree, egg and egg yolk- whisk until no lumps remain.
In a medium bowl, whisk together the flour, baking soda, pumpkin pie spice, cinnamon and cream of tartar. Add the wet ingredients to the dry ingredients and stir by hand until cookie dough is formed then add in white chocolate chips.
Cover bowl with plastic wrap and place in the refrigerator to chill for 20 minutes or up to 3 days.
When ready to bake cookies, preheat oven to 350 degrees F and line two baking sheets with parchment paper or silpat mats.
Use a small ice cream scoop, or portioning out 2 tablespoons of cookie dough per cookie. In a shallow dish or small bowl, combine the granulated sugar and cinnamon together. Roll into a ball and then roll into the cinnamon sugar mixture to coat the entire dough ball. Arrange cookies on the baking sheets and press down on the cookie with your hand as the cookies will only spread a tiny bit when baking. I love studding the tops with more white chocolate chips.
Bake for 9-10 minutes. They will seem under baked but they will cook more as they cool. Sprinkle any remaining cinnamon sugar mixture on top while the cookies are fresh out of the oven. Place the baking sheets on a wire rack or cool surface to cool for a few minutes. Then remove the cookies from the baking sheet and place on wire rack to cool completely. Enjoy!