Preheat the oven to 190 degrees celsius while mixing the ingredients.
Put caster sugar into a mixing bowl and mix together with the butter using a fork. (the fork is much better than a spoon it removes the lumps quicker and binds everything evenly).
Sift in flour, xantham gum, cocoa powder and baking powder.
Mix all together with a fork tipping bowl to a 45 degree angle until eveything is mixed together. This should add some air bubbles to the mixture and should after 2 minutes standing look a little like chocolate moose.
Divide out the mixture into bun cases and bake in the oven for 15 minutes at 190 degrees celsius.
You can top with anything you like and enjoy. They are great warm and cold.