Using a mixer, cream butter and sugars in a large mixing bowl.
Add egg and vanilla and beat again until well combined, scraping sides of bowl as needed.
Add gluten free baking mix in two batches and mix again. It won't be so thick that you can't continue mixing it, but it should appear "doughy."
Stir in chocolate chips, cover and refrigerate overnight or for at least 4-6 hours until thoroughly chilled. You should be able to roll the dough into balls before baking.
Preheat oven to 350 degrees F (176 C).
Once chilled, scoop out rounded Tablespoon amounts of dough, roll them into balls and place them 2 inches apart on a baking sheet.
Bake for 8-10 minutes or until the edges are just slightly golden brown. Remove from oven and let rest on the pan for 5 minutes, then transfer to a cooling rack. Store leftovers in an airtight container at room temperature for up to several days. Freezer for longer term storage. (They taste just as good the 2nd and 3rd day as they hold their texture/flavor well.)
*Adapted from (the amazing) Martha Stewart *I have not tried this recipe with any other gluten-free flours or mixes, so be sure to use the mix I list! *Nutrition information is a rough estimate.