Preheat your oven to 350°F (175°C) and line the muffin tin with paper liners or grease with cooking spray.
In a large mixing bowl, whisk together the flour, cocoa powder, granulated sugar, brown sugar, baking powder, baking soda, and salt until well combined.
In another bowl, whisk the eggs, milk, vegetable oil, and vanilla extract together until smooth.
Pour the wet ingredients into the dry ingredients and gently mix until just combined. Be careful not to overmix; a few lumps are okay.
Fold in the chocolate chips using a rubber spatula, ensuring they are evenly distributed in the batter.
Divide the batter evenly into the prepared muffin tin, filling each cup about 2/3 full.
Bake for 18 to 20 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
Remove the muffins from the oven and allow them to cool in the muffin tin for about 5 minutes before transferring them to a cooling rack to cool completely.