Preheat oven to 375ºF.
Grease 12 inch pizza pan with butter.
Sift flour, xantham gum, baking soda, and salt together.*Optional Make your own brown sugar: mix 3/4 cup granulated sugar and 1 1/2 tsp molasses together using a fork. (See pic above) I highly recommend but if you do not have molasses then use 3/4 cup of store bought brown sugar.
Using a mixer (handheld or stand) mix flour mixture with softened butter. Once mixed well add the following in this order: sugar mixture, egg, and then vanilla extract. Beat until dough forms.
Add chocolate chips and mix well.
Try to make a large ball with cookie dough. Place ball in the middle of the pan. Spread out evenly, but leave 1 1/2-2 inches from the edge.
Bake for 15-17 minutes, or until golden brown.
Allow to cool then add icing/decorations of your choice.