Preheat the oven to 400℉. Lightly spray 48 mini muffin cavities with cooking spray and set aside.
In a large bowl, mix together the flour, sugars, baking powder, cocoa powder and salt.
In a small bowl, mix together the egg, milk, vanilla and oil.
Slowly mix the wet ingredients into the dry ingredients until just combined. Fold in the chocolate chips.
Divide the batter evenly into the prepared muffin pan and bake in the preheated oven for 10 minutes. Allow to cool completely in the muffin tins before transferring to an airtight container.