Preheat your oven to 375 degrees F.
In a large bowl, whisk the oil, eggs, vanilla, sugar and pumpkin.
Use a spatula to fold in your sourdough starter.
Add the flour, salt, baking powder, baking soda and pumpkin pie spice. Mix until just combined (don't overmix).
Gently fold in the chocolate chips.
Grease a muffin tin with coconut oil.
Pour the batter into the muffin tin filling about 3/4 full.
Mix the sugar and pumpkin spice in a small bowl.
Sprinkle the pumpkin spice sugar over the sourdough pumpkin muffin batter.
Bake for about 20 mins or until a toothpick inserted into the center of the muffins comes out clean.
Cool for about 5 minutes until the muffins loosen from the muffin tin and then rest on a cooling rack.
Store in an airtight container at room temperature for about 3 days or freeze for up to 3 months.