Preheat oven to 400 degrees Fahrenheit.

Spray 12 standard muffin cups with nonstick cooking spray.

In a large bowl, whisk together the flour, cocoa powder, sugar, baking soda, and salt, until well blended.

In another bowl, whisk together the milk, oil, eggs, and vanilla extract.

Add liquid ingredients into the dry ingredients and using a rubber spatula, gently blend all ingredients until just combined.

Gently blend in the ½ cup of semi-sweet chocolate chips into the batter.

Using an ice cream scoop, divide batter evenly into the muffin cups. Sprinkle mini chips evenly over each muffin.

Bake for approximately 20 minutes, or until a small, sharp knife inserted into the center comes out clean.

Cool muffins for 5 minutes before removing from the muffin pan.