Preheat the oven to 200°C (392°F)
In a bowl, sift and add the white rice flour, tapioca flour, corn starch, and brown rice flour. Then add the granulated white sugar, dark brown sugar, xanthan gum, cocoa powder, baking powder, baking soda, salt, and semi-sweet chocolate chips. Using a whisk, combine the ingredients.
In a separate bowl, add the eggs, sour cream, vegetable oil, milk, vanilla extract, and instant coffee. Using a whisk, combine the ingredients.
Then, add the egg mixture to the flour mixture and gently mix using a spatula until combined. The batter will be thick.
Align a cupcake tin with cupcake liners and fill each liner all the way to the top with the gluten free chocolate muffin batter. Optional: Add extra chocolate chips to the top of each muffin.
Bake the muffins at 200°C (392°F) for 5 minutes, then reduce the oven temperature to 180°C (356 °F) and bake for another 13-15 minutes or until a toothpick inserted at the center comes out with little to no crumbs ( having a few crumbs and chocolate smudge on the toothpick is fine). Allow the gluten free chocolate muffins to cool down in the cupcake tin for 5 minutes before transferring them to a cooling rack.