1. In a large bowl, mix flour, starter, and oil together until combined. Cover it and let it rest at least 6 hours or overnight in the refrigerator.2. In a medium size bowl, mix sugar, eggs, vanilla, and cocoa. Then add milk and mix until combined.3. In a stand mixer or large bowl, add the overnight sourdough mixture and the cocoa powder. Using the whisk attachment, mix until combined. Then add the salt and baking soda and mix until combined.4. Preheat your oven to 350 degrees. Prep your muffin tin by putting the muffin liners and spraying with oil if you want to. Bake for 15 minutes, until a toothpick comes out clean. Allow them to cool before topping with buttercream frosting and enjoy!