Preheat the oven to 375℉. Lightly spray a muffin pan with cooking spray and set aside.
In a large bowl, mix together the eggs, oil, yogurt, coffee and vanilla until fully combined.
In a separate bowl, mix together the flour, cocoa powder, baking soda and salt.
Slowly mix the dry ingredients into the wet ingredients until just combined. Fold in the chocolate chips.
Divide the mixture into the prepared muffin pan and bake in the preheated oven for 15 minutes, or until a toothpick inserted into the center of a muffin comes out clean. Allow to cool in the pan for around 5 minutes, then transfer to a wire rack to cool completely.