Over medium low heat, Melt butter in small saucepan. Stir frequently as it transitions from bubbling to foaming. Once you see a golden brown color sneek through the foam, stir briefly and remove from heat. Pour it into a glass measuring cup to cool for about 15 minutes before using in the recipe. Whisk it occasionally to help with the cooling process while you gather the other ingredients.
* Egg and pumpkin puree should be at room temperature before combining mixture.
Preheat oven to 350℉.
In a medium bowl, add the sugars and whisk together to combine. Set aside to wait for browned butter to be cooled sufficiently before using.
In a small bowl, whisk together the dry ingredients and set aside.
Add the cooled browned butter to the sugars and whisk to blend in.
Add in the pumpkin puree until well combined.
Whisk in egg YOLK and vanilla.
Using a spatula or wooden spoon, stir in dry ingredients until no remnants of flour are visible.
Cover and refrigerate for a couple of hours.
Scoop with a 1-1/2 T cookie scoop onto a rimmed cookie sheet lined with parchment paper 2" apart.
Roll each scoop into a ball and then into the spiced sugar mixture to thoroughly coat. Return to the cookie sheet.
**Keep the remainder of the dough chilled until you are ready to prep the second pan.
Bake in a 350℉ oven on the middle rack for 12 minutes.
Place cookie sheet on a cooling rack. Allow cookies to completely cool before removing from pan.
Once cooled, place in a storage container or plastic bag.