Step 1

Preheat the oven to 350 degrees F. Line 12 muffin cups with paper liners.

Step 2

Whisk together the flour, cocoa powder, baking powder, baking soda and salt in a large bowl. Stir in the chocolate chips. In a medium bowl, whisk together the milk, brown sugar, butter, oil, vanilla and eggs until smooth.

Step 3

Quickly fold the milk mixture into the flour mixture with a rubber spatula. Divide the batter evenly among the prepared muffin cups. Bake until a toothpick inserted in the center comes out clean, about 25 minutes. Transfer the muffins from the pan to a wire rack to cool.