** if you don't have greek yogurt substitute with 1/2 buttermilk (make your own - in a half cup measurement add 1/2 tablespoon lemon juice and top up (to remaining half cup) with milk, let sit 15 minutes.
Pre-heat oven to 400° (200° celsius), grease and flour a 6 or 12 muffin tin.
In a large bowl whisk together flour, sugar, chocolate chips, cocoa powder, baking soda, baking powder and salt until combined.
In a medium bowl whisk together egg, yogurt, milk, vanilla, coffee and oil until combined.
Pour wet mixture into dry mixture and stir just until combined (stir approximately 18 times).
Fill muffin tins almost to the top. Sprinkle with a few extra chips if desired.
Bake at 400° (200° celsius) for 5 minutes, then lower heat to 350° (175° celsius) and continue to bake for approximately 15 minutes or until toothpick comes out dry and clean. Let cool completely. Enjoy!