Preheat oven to 425F (220C) and line a muffin tin with paper liners. Set aside.

In a large mixing bowl, whisk together flour, sugar, baking soda, baking powder, and salt until well-combined.

In a large measuring cup (or a separate mixing bowl), combine the hot water, cocoa, and instant coffee (if using). Whisk until smooth.

Add sour cream, avocado oil, egg, and vanilla extract and whisk well.

Add sourdough discard to the measuring cup and whisk until ingredients are well incorporated.

Add wet ingredients to the flour mixture and use a spatula to gently fold together until about halfway combined. Add chocolate chips and continue to fold until ingredients are just combined.

Divide batter into prepared muffin tin, filling each liner nearly to the rim. Note that this recipe makes 18 muffins, if you only have a single 12-count liner it is fine for the batter to sit, covered, on the counter, while the first batch bakes.

Sprinkle muffins with additional chocolate chips, if desired, and transfer to center rack of 425F (220C) oven. Bake for 8 minutes, then, without opening the oven door, reduce oven temperature to 350F (175C) and continue to bake for 9-10 minutes longer or until a toothpick inserted in the center comes out clean or with moist/fudgy crumbs (not wet batter).

Allow muffins to cool for 5-10 minutes in the muffin tin before gently removing from the tin (careful, the tin is hot! I use a butter knife to gently pry up each muffin) and transferring to a cooling rack to cool completely.