This is my most-coveted Christmas cookie. Amounts following ingredients are for a double batch, which is all I make.
1.75 cups (8 3/4 oz) flour (1 lb 1 1/2 oz)
.25 cups (1 3/8 oz) rice flour (2 5/8 oz)
.67 cups (4 3/4 oz) superfine sugar (9 1/2 oz)
.25 t. salt (1/5 tsp)
16 Tbs (8 oz) cold, unsalted butter (16 oz)
1 tsp sugar for sprinkling (2 tsp)
Preheat oven to 425F. Line ungreased 9-inch round cake pan with parchment of wax paper; set aside
In bowl of standing mixer fitted with paddle attachment, mix flours, sugar, and salt at low speed until combined, about 5 seconds. Cut butter into .5″ cubes with .25 cup flour mixture on a sheet of parchment paper. Add butter and any remaining flour on parchment to bowl with dry ingredients. Mix on low speed until dough is pale yellow and resembles damp crumbs, about 4 minutes.
Press dough into pan. (With my pans, a single batch is 2 lb 3 oz–useful info for splitting the double batch.) Unmold onto cookie sheet, use 2″ cookie cutter to remove center and set aside on cookie sheet. Replace cookie cutter. Place shortbread in oven, immediately reducing temperature to 300F.
Bake 20 minutes, remove from oven, score into 16 wedges and poke design with skewer. Bake an additional 40 minutes until pale golden. Cut on score marks, slide shortbread onto rack and cool thoroughly.