Begin by preheating your oven to 350 degrees Fahrenheit (190 degrees Celsius). Then, line (or grease lightly) your muffin tin and set aside.
Next, whisk together the baking powder, baking soda, salt, flour, ground espresso, and cinnamon in a medium bowl and set aside.
In a large bowl, or stand mixer with whisk attachment, whisk together the sourdough discard, vanilla extract, coconut oil, egg, sour cream, milk, and sugar until smooth. If using a stand mixer, set the mixer to a low speed to prevent overmixing.
Then, gradually add the dry ingredients to the wet ingredients. Be careful not to overmix.
Next, fold in the chocolate chips and spoon the muffin batter into the muffin tin. Fill each cavity in the tin about 2/3 of the way full. Top with extra chocolate chips.
Bake the muffins for 18-22 minutes or until a knife or toothpick comes out clean if inserted into the middle of a muffin. Let cool down for at least 5 minutes and then enjoy! This makes about 24 muffins.