Blot the pumpkin with a paper towel to remove excess moisture. Set aside.
Whisk together the flour, cornstarch, cream of tartar, baking soda, salt, 2 teaspoons cinnamon, nutmeg & ground cloves. Set aside.
In a separate large bowl beat together the butter and ¾ cup brown sugar and ¾ cup granulated sugar until fluffy.
Beat the pumpkin, egg yolk and vanilla extract into the butter mixture until combined.
Mix the dry ingredients into the butter mixture. The dough will be thick.
Cover the bowl with clingfilm and refrigerate for at least 2 hours or up to 2 days.
When ready to bake, preheat the oven to 350℉ (180℃) and line cookie trays with parchment paper or silicone baking mats.
Whisk together the ¼ cup granulated sugar and 1½ teaspoons cinnamon and pour onto a small plate or shallow bowl. Scoop out the cookie dough and roll into balls with about 1-1½ tablespoons of dough each. Roll each dough ball in cinnamon sugar and place about 2 inches (5 cm) apart on the lined cookie sheets.
Bake 1 sheet at a time in the middle of the preheated oven for about 9-12 minutes, or until the tops look set. Remove from the oven and cool on the cookie sheet for at least 10 minutes.