Preheat oven to 350 degrees Fahrenheit. Line a muffin pan with liners or spray generously with baking spray.

In a mixing bowl, combine flour, cocoa, baking powder, baking soda, salt and coffee.

In another bowl (or measuring cup), whisk together sugar and eggs, then add oil, vanilla and yogurt.

Combine wet and dry ingredients. Fold in chocolate chips.

I find that baking time varies greatly, from 20 to 35 minutes, depending on the size and weight of your muffin pan. Bake until center is firm and bouncy to the touch.