Preheat the oven to 400°F and line a 12-cup muffin tin with paper liners or spray generously with gluten-free nonstick cooking spray.
In a large bowl, whisk together the flour, cocoa powder, xanthan gum, sugar, baking powder, baking soda, and salt. Stir in the chocolate chips, then set aside.
In a medium bowl, whisk together the eggs, milk, oil, vinegar, and vanilla extract. Pour the wet ingredients into the dry ingredients and stir until combined.
Use a large scoop to transfer and divide the batter evenly between the 12 muffin cups. Sprinkle a few additional chocolate chips on top of the muffins and gently press in, if desired.
Bake the muffins for 15-18 minutes or until done. Cool in the pan for 5 minutes, then transfer to a wire rack. Serve warm or at room temperature.
1. If your flour blend contains xanthan gum, omit what’s called for in the recipe.
2. ½ cup mini chocolate chips can be used instead.
3. To make these muffins dairy-free, use unsweetened coconut milk beverage in place of the milk and use dairy-free chocolate chips.
4. Store muffins in an airtight container for up to 2 days. These muffins freeze well. Store in a freezer bag and defrost at room temperature.