Make sure your butter has reached room temperature. Add your butter and white sugar to a bowl and cream for 2 minutes on high until pale and creamy.
¾ cup (170g) unsalted butter, softened, 1 ¼ cups (250g) white sugar
Blot any excess water from your pumpkin puree.
Add in your pumpkin puree, egg, sourdough discard, and vanilla. Mix with your hand beaters or stand mixer on medium speed until well incorporated.
⅔ cup (135g) pumpkin purée, 1 egg, 1 ½ tsp vanilla extract, ½ cup (120g) sourdough discard, unfed
Whisk together your flour, cream of tartar, cornstarch, baking soda, salt, cinnamon, ginger, nutmeg, and cardamom.
3 ½ cups (420g) all-purpose flour, 2 tsp cream of tartar, 1 tsp baking soda, 2 tsp ground cinnamon, ½ tsp ground ginger, ¼ tsp ground nutmeg, ⅛ tsp ground cardamom, ¾ tsp salt, 1 ½ Tbsp (12g) cornstarch
Add the dry ingredients to the wet, and mix gently until the dough is mixed and no streaks remain. Be careful not to overmix the dough at this point, or the cookies will be tough.
Scoop your cookies into 1/4 cup balls and transfer to a parchment lined cookie sheet. Chill the dough at least two hours, optimally overnight so they're easiest to shape. If the dough is too wet to scoop, chill for 20-30 minutes first then scoop and chill.