Preheat oven to 400°F (200℃) and line a 12-cup muffin pan with muffin liners*. Set aside.
In a small bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
In a large bowl, use a hand-held blender on medium speed to cream together the softened butter and granulated sugar until light and fluffy, about 2-3 minutes.
Add the sourdough discard, eggs, vegetable oil, yogurt, and vanilla extract. Mix until smooth and combined. Fold the dry ingredients into the wet ingredients and stir until almost no dry spots remain. Fold the chocolate chips into the batter, mixing until just combined.
Spoon the batter into the prepared muffin liners, filling each cup about ⅔ full (a cookie scoop works well for this!). Depending on the size of your muffin cups, you might find that you have enough batter for an extra muffin.
Sprinkle with additional chocolate chips (optional) and turbinado sugar. Bake for 24-26 minutes until golden brown. Let the muffins cool in the pan for 10 minutes, then transfer to a cooling rack to cool fully.
Notes
1 serving = 1 muffin. To make this recipe with active sourdough starter, replace the sourdough discard with active starter (200g). You do not need to make any other changes to the recipe.