Whisk together egg, and sugar until combined.
Whisk in yogurt, oil, and starter.
In a separate bowl whisk flour and cocoa powder together.
Add dry ingredients to wet ingredients. Mix everything together with a rubber spatula.
Cover with plastic wrap and let it sit at room temperature for 8 hours to ferment. (can ferment up to 16 hours)
After fermentation, Preheat the oven to 400℉ degrees with the baking rack in center position. Line a standard muffin pan with parchment paper liners and set aside.
Add baking soda, baking powder, salt and vanilla to the fermented batter. Mix until fully incorporated.
Add in chocolate chips and fold them really gently in the batter.
Spoon batter into prepared muffin tins using a ¼ cup scooper. Sprinkle a few chocolate chips on top of each one if you want even more chocolate flavor!
Place them in the oven and reduce the heat to 375℉ , bake for about 15-20 minutes or until the toothpick inserted in the center comes out clean.
Cool for 5 minutes in the pan then remove muffins and cool on a wire rack.