Preheat your oven to 350 degrees F and line a muffin tin with paper liners or lightly grease with cooking spray.
In a large mixing bowl, combine the melted butter, white sugar, eggs, vanilla extract and milk.
In a separate bowl, whisk together the gluten-free flour, cocoa powder, baking powder, baking soda, and salt until well combined.
Gradually add the wet ingredients to the dry ingredients and mix until just combined. Be careful not to overmix!
Gently fold in the chocolate chips until evenly distributed throughout the batter.
Divide the batter evenly among the prepared muffin cups, filling each about 3/4 full.
Bake in the preheated oven for 20-25 minutes, or until a toothpick inserted into the center of a muffin comes out clean or with a few moist crumbs.
Allow the muffins to cool in the pan for a few minutes before transferring them to a wire rack to cool completely. Or, if you're anything like me, dive right in while they're still warm and gooey!