Preheat oven to 350°F. Line baking sheet with parchment paper. In small bowl, whisk together white rice flour, sweet rice flour, cornstarch, baking soda, and salt. In another small bowl, cream together sugars and butter until a thick paste forms. (Use a wooden spoon or handheld mixer. This batch is too small for a stand mixer.) Add the egg. Beat until smooth. Add dry ingredients. Mix until a dough forms. Add chocolate chips. Stir to combine.