In a large mixing bowl, use electric mixer to beat butter (or margarine), sugars, and vanilla extract together until smooth. beat in egg.

In separate bowl, whisk together flours, soda, xanthan gum, and salt. beat into egg mixture on low speed until incorporated. Dough will be somewhat stiff. Stir in chocolate chips.

Drop by tablespoons (or use a small spring-action ice cream scoop for evenly sized cookies) onto nonstick cookie sheet lined with parchment paper or nonstick liners--or sprayed with cooking spray. Bake for 10-12 minutes or until cookies are lightly puffed and slightly browned. Cool on wire rack. Store in airtight container.