Preheat your oven to 425°F and prepare a 12-cup muffin pan with liners.
In a large mixing bowl, whisk together the wet ingredients (oil, sugar, milk, eggs, sour cream, sourdough discard, and vanilla).
200 g granulated sugar, 2 eggs, 185 g sour cream, 120 ml vegetable oil, 80 g whole milk, 100 g sourdough discard, 2 teaspoons vanilla extract
In a separate bowl, mix the flour, baking powder, baking soda, cocoa powder, and salt.
240 g all-purpose flour, 42 g cocoa powder, 1 teaspoon baking soda, ½ teaspoon baking powder, ½ teaspoon salt
Add the dry ingredients to the wet ingredients and whisk until just combined. Stir in the chocolate chips.
255 g chocolate chips
Using a 3-tablespoon cookie scoop, divide the batter between the 12 muffin cups, filling to the top. Bake at 425°F for 5 minutes, then reduce to 350°F and bake another 12–15 minutes, until domed and slightly firm to the touch. Do not open the door when changing the temperature.
Notes
Tip: To long-ferment these muffins for extra sourdough flavor, add the baking powder and baking soda last (right before baking).Tip: Take the muffins out when they look just done (no wet batter on top) — fully baked but not overbaked. Pulling them too early can cause the tops to sink while cooling.Tip: For the best, most consistent results, use a kitchen scale to weigh your ingredients.