Preheat the oven to 425 °F and set an oven rack in the middle position. Spray a 12-cup muffin pan with nonstick cooking spray. In a medium bowl, sift the flour, cocoa, baking powder, and baking soda. In a large bowl, whisk together the melted butter or avocado oil, salt, sugars, and vanilla until combined. Whisk in the eggs until blended, followed by the buttermilk.

Add the dry ingredients and fold until just combined. Stir in ¾ cup of the chocolate chips. Spoon the batter evenly into the prepared pan, filling the muffin cups full.

Sprinkle the remaining ¼ cup chocolate chip evenly over the muffin tops, pressing them lightly into the batter. Place in the oven and bake for 8 minutes, then turn the oven down to 350 °F and bake for about 12 minutes more, or until a toothpick inserted in the center of a muffin comes out clean *(check a few spots as the melted chocolate chips will make the tester look wet).

Transfer to a wire rack and let cool for about 5 minutes before removing the muffins from the pan; cool the Chocolate Muffins on a rack.