01 -  Preheat the oven to 375°F. Line a 12-cup muffin tin with paper liners or grease lightly. 
 02 -  In a large bowl, whisk together pumpkin purée, granulated sugar, brown sugar, eggs, oil, sourdough starter, and vanilla extract until the mixture is smooth. 
 03 -  In a separate bowl, whisk together flour, baking soda, baking powder, salt, cinnamon, nutmeg, cloves, and ginger. 
 04 -  Add the dry ingredient mixture to the wet ingredients and fold gently with a spatula until just combined. Avoid overmixing. 
 05 -  Fold in the dark chocolate chips until evenly distributed throughout the batter. 
 06 -  Divide the batter evenly among the muffin cups, filling each about three-quarters full. 
 07 -  Bake for 20 to 22 minutes or until a toothpick inserted into the center comes out clean or with a few moist crumbs. 
 08 -  Let the muffins cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.