Preheat oven to 450 degrees. Prepare a cookie sheet and line it with a piece of parchment. On top of the parchment, place a 9 or 10" springform RING - you do not need the bottom of the pan. In a mixer, blend all dry ingredients. Slowly add butter, blending until incorporated - 5 to 10 minutes - until the mixture looks like clumps. Sprinkle mixture inside the closed springform ring and press down into a solid 1/2" disk. Smooth with the back of a spoon. Use a 2" round cookie cutter to remove the center of the disk of dough - this allows for dough to bake evenly so center is not undercooked. Remove 2" circle of dough and replace cookie cutter so that the shortbread does not spread into that area. Also release the lock on the springform ring, allowing for dough to spread outward slightly during the baking process. Bake for 5 minutes only at 450 degress, then turn heat down to 250 degrees and bake for 10 to 15 minutes, until the top barely becomes golden. Turn oven OFF, but it should remain closed. Take springform ring and cookie cutter off of dough. Using a large, sharp knife, score the dough into wedges HALF WAY through the dough. Also poke each wedge with a skewer 8 to 10 times to release steam. Return to over that is turned OFF, with a wooden spoon keeping the door slightly ajar. Cookie should remain in the oven for 1 hour. Remove from oven and cool for a full 2 hours, then cut into wedges and enjoy. Store in an airtight container.