Preheat the oven to 375°F (190°C). Line a 12-cup muffin pan with paper liners or lightly grease it.
Mix the dry ingredients.
In a large bowl, whisk together the flour, cocoa powder, granulated sugar, brown sugar, baking powder, baking soda, and salt until well combined.
Add the wet ingredients.
Add the eggs, milk, vegetable oil, and vanilla extract to the bowl. Gently mix until just combined. Do not overmix.
Fold in the chocolate chips.
Using a spatula, gently fold in the chocolate chips, reserving a few for topping if desired.
Fill the muffin pan.
Divide the batter evenly among the muffin cups, filling each about ¾ full. Sprinkle the reserved chocolate chips on top.
Bake.
Bake for 18–22 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.
Cool and serve.
Let the muffins cool in the pan for 5 minutes, then transfer to a wire rack to cool completely before serving.