½ cups old fashioned rolled oats
1½ cups unbleached all purpose flour
¼ cup sornstarch
⅔ cup confectioners sugar
½ tbp table salt
14 tbp ! ¾ sticks unsalted butter, cold cut into ⅛ inch thick slices
Heat oven to 450 degrees Pulse oats in spice grinder or blender until reduce to fine powder, about ten 5 second pulses. In bowl of stand mixer fitted with paddle attachment mix oat flour all purpose flour cornstarch sugar and salt on low speed until combined about 5 seconds. Add butter to dry ingredients and continue to mix on low speed until dough forms and pulls away from sides of bowl 5 to 10 minutes. Bake shortbread 5 minutes, then reduce oven temp to 250 degrees. Continue to bake until edges turn pale golden 10 to 15 minutes longer. Remove baking sheet from oven: turn off oven. Remove spring form pan collar; use chef's knife to score surface of shortbread into 16 even wedges cutting halfway through shortbread. using wooden skewer poke 8 to 10 holes in each wedge. Return shortbread to oven and propel door open with handle of wooden spoon leaving 1 inch gap on top. Allow shortbread to dry in turned off oven until pale golden in center (shortbread should be firm but giving to touch), about 1 hour. Transfer baking sheet to wire rack; cool shortbread to room temperature at least 2 hours. Cut shortbread at scored marks to separate and serve.