Preheat the oven to 220ºC/425ºF conventional oven. Prepare two muffin pans with 6 muffin liners, only lining every other cupcake hole, as it helps them to dome up.
Note: If you want smaller muffins, use two 12-cup cupcake pan with 12 cupcake liners, only lining every other cupcake hole, as it helps them to dome up.
In a large mixing bowl add cocoa powder and coffee (or milk) and whisk together until a paste.
50 g unsweetened dutch process cocoa powder, 60 g coffee or milk
Then add the Greek yogurt and whisk it together until combined.
240 g Greek yogurt
Continue by adding the granulated sugar and eggs and whisk it together until combined.
200 g granulated sugar, 2 large eggs
Then add the oil and vanilla extract and whisk until combined.
120 g vegetable oil, 2 teaspoon vanilla extract
Place a sieve on the bowl and sift in the all-purpose flour, baking powder, baking soda and salt together. Stir the dry ingredients into the batter.
270 g all-purpose flour, 2 teaspoon baking powder, ½ teaspoon baking soda, ½ teaspoon salt
Add the chocolate chips and gently fold it into the batter using a rubber spatula.
150 g chocolate chips
Let the batter rest for 10 minutes.
Divide the cake batter into the 6 muffin liners. Top the muffins with the chocolate chips and bake them for 7 minutes and then reduce the heat to 175ºC/350ºF (without opening the oven) and further bake for 17-18 minutes. (Note: If making them in a cupcake pan they need 7 minutes on 220ºC/425ºF and then reduce the heat to 175ºC/350ºF and further bake for 10 -13 minutes).
Let the muffins cool in the hot pan on a wire rack. After 5 minutes, remove the muffins from the pan and let them cool down additionally for 15-20 minutes before eating.