Preheat your oven to 350°F (175°C) and line your muffin tin with papers or grease it lightly.
In a mixing bowl, whisk together the all-purpose flour, cocoa powder, baking soda, baking powder, and salt until well combined.
In another bowl, combine the granulated sugar with the sour cream (or yogurt), egg white, coffee (or milk), vegetable oil, and vanilla extract. Stir until smooth.
Gradually add the dry mixture to the wet ingredients, stirring until just combined. Avoid overmixing.
Gently fold in the chocolate chips until evenly distributed.
Spoon the batter into the prepared muffin tin, filling each cup about 3/4 full. Optionally, sprinkle extra chocolate chips on top.
Bake in the preheated oven for 15-18 minutes, or until a toothpick inserted comes out clean.
Let the muffins cool in the tin for a few minutes before transferring to a wire rack to cool completely. Enjoy!
