Preheat your oven to 400 degrees. Line muffin pan with paper liners and spray with non-stick spray.
In a large mixing bowl, combine together the flour, Stevia, baking powder, baking soda, and unsweetened cocoa. Set aside.
In a medium bowl, whisk together the vegetable oil, milk, vanilla, and egg.
Add the wet ingredients into the bowl of dry ingredients and blend together.
Then gently fold in the chocolate chips.
Fill each muffin cup about 2/3 of the way and then top with additional chocolate chips.
Bake for 18-20 minutes. Allow the muffins to cool for 10-15 minutes before removing muffins from the pan.