Preheat your oven to 350°F (175°C). Line a muffin pan with muffin liners or grease the muffin cups.
In a large bowl, whisk together the pumpkin puree, sourdough discard, eggs, oil, white sugar, brown sugar, and vanilla extract until smooth.
In a small bowl, mix the flour, pumpkin pie spice, baking powder, baking soda, and salt.
Add the dry ingredients to the wet ingredients and stir gently until just combined. Don’t overmix! Fold in chocolate chips or nuts if using.
Spoon the batter into the prepared muffin cups, filling each about ¾ full.
Bake for 18 - 20 minutes, until the tops are set and a toothpick or cake tester comes out clean.
Cool in the pan for 5 minutes, then transfer muffins to a wire rack to cool completely.