Prepare 2 baking pans lined with parchment paper. With an electric mixer, cream butter and organic sugar together in a bowl. Gradually add egg and vanilla while mixing. Add flours and salt, mix and then lightly mold the mixture together with your hands. Turn dough out onto a floured surface, knead lightly and roll dough with your hands into a 14-inch-long log. Wrap in plastic wrap; chill for 1 hour. While the dough is chilling, finely chop the pistachios and combine them with the turbinado sugar on a tray; set aside.

Preheat the oven to 325 degerees. Brush shortbread log with milk and roll it firmly in the sugar-nut mixture until completely covered. Cut into 28 1/2-inch discs and place on baking pans, leaving 1-1/2 inch between each one. Bake on middle and top shelves of oven 15 to 18 minutes, or until very pale golden, swapping the pans halfway through. Remove and cool on a wire rack.