From the gluten-free blog Karina's Kitchen, my wife and I have slightly adapted her Mint Chocolate Chip cookie recipe.
Preheat oven to 350 degrees.
In a large mixing bowl or stand mixer combine:
Mix well. Then add the dry ingredients, not mixing until all are added to keep the xanthan gum dry until mixing:
Bake on a cookie sheet for about 15 minutes. Cookies are done when the top surface pops back up after being pressed lightly.
Cookies bake best when on a silicon mat and pressed somewhat flat (by hand with wet fingers works fine) before baking. Also works as a large bar cookie.
To make these Passover safe, use three eggs; omit the baking powder and baking soda and instead give "lift" by separating the eggs, whipping the egg whites, and folding the egg whites in as the last step before baking. This works very well.