Preheat the oven to 350°F (175°C) and line a muffin tin with paper liners.

Whisk together the dry ingredients in a large bowl: flour, cocoa powder, sugar, baking powder, baking soda, and salt.

Combine the wet ingredients in another bowl: vegetable oil, eggs, vanilla extract, and buttermilk.

Pour the wet ingredients into the dry ingredients, stirring gently until just combined.

Fold in the chocolate chips.

Divide the batter evenly among the muffin cups, filling each about 2/3 full.

Bake for 18-20 minutes until a toothpick inserted in the center comes out clean.

Cool the muffins in the tin for a few minutes before transferring them to a wire rack.