In a large bowl, whisk together the flour, sugar, cocoa powder, espresso powder, baking soda, baking powder, and salt.

Mix the wet ingredients

In a separate bowl, whisk together the eggs, sour cream, vegetable oil, milk, sourdough discard, and vanilla extract until smooth.

Pour the wet ingredients into the dry ingredients and gently mix until just combined. Don’t overmix—lumpy batter is your friend here.

Fold in the chocolate chips like the generous, chocolate-loving person you are.

The overnight magic (don’t skip this if you can help it)

Cover the bowl and place the batter in the fridge overnight.

The next day, preheat your oven to 375°F (190°C). Line a muffin tin (even if they’re not bakery-sized… we persevere).

Scoop the batter into the muffin cups, filling them about ¾ full. Sprinkle the tops with turbinado sugar.

Bake for 18–22 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs (not wet batter).