Preheat oven to 425F and line a muffin tin with papers.

Sift the flour, cocoa powder, baking soda, baking powder, salt, and sugar into a large bowl. Whisk together and set aside.

In a separate bowl, combine the eggs, vanilla, vegetable oil, sour cream, and milk, then whisk together.

Set aside about 1/3 cup of the chocolate chips for the muffin tops.

Pour the wet ingredients into the dry ingredients and fold together using a spatula, mixing until almost combined. Sprinkle in the remaining chocolate chips and mix until the batter is just combined.

Fill the muffin papers to the top and sprinkle with the reserved chocolate chips.

Bake at 425F for 6 minutes, then reduce temperature to 350F and continue baking for about 14 minutes or until the centers are set and a toothpick inserted in the center comes out clean.