Preheat oven to 350 degrees. Line 2 large baking sheets with parchment paper. Sift the dry ingredients except the xanthan gum into a large mixing bowl until there are no lumps
Stir in the eggs, butter and extract until a smooth dough forms. Sprinkle in the xanthan gum until fully combined and smooth. Scrape down the sides of the bowl and push the dough to the center of the bowl
Massage the ball in hands to make sure of the texture. the dough should be smooth and hold its shape well. Form the dough back into a ball and divide into 2 portions. Set one portion aside and place the other portion back into the mixing bowl
Break the dough portion that is in the bowl up a little. Gradually stir in the cocoa powder until fully combined. Scoop the dough out by teaspoonfuls and place onto a lined worksurface. Roll each of the scoops into small smooth dough balls
Do this with both portions of the dough. Make sure dough stays smooth at all times. To form the cookies, take 3 balls of the chocolate portion and 3 ball of the vanilla portion and form into a tight circle. Alternate the colors and keep the dough balls connected.
Gently press the small dough balls together to form a single dough ball. Make sure to smooth out all the cracks. Roll the ball a couple times in hands to create a smooth swirl in the dough ball. (see video if needed)
Place the shaped dough ball onto the prepared baking sheet and gently flatten the top to form a disc shape. The flatter the cookie is pressed the firmer the cookie will be once it cools If there are any cracks dampen fingers and rub out the cracks
Repeat the forming process until all the dough is formed and on the baking sheets. Place in the preheated oven. Bake at 350 degrees 12 to 15 minutes or until lightly golden around the edges
Remove from the oven and allow to cool on the pan at least 10 minutes to firm up. Once firm remove from the pan and transfer to a wire rack to cool completely before serving