Preheat oven to 350° and place paper baking cups into 24 regular-sized muffin cups.
In a medium bowl, mix flour, cocoa powder, baking soda, and salt.
In a large bowl, cream sugar, oil, and egg.
Next, add vanilla extract.
On a low speed, alternate blending in dry mixture and milk.
Fill each muffin cup up about 2/3 full and bake for 20-25 minutes until an inserted toothpick comes out clean. Cool thoroughly before filling.