- 9" round cake pan
- smaller round cake pan
- Rimless baking sheet (or an inverted baking sheet)
- 2" biscuit cutter
- Parchment paper
- 1 3/4 cups (8.75 oz) unbleached all-purpose flour (preferably with a protein content no higher than 10.5 percent - Gold Medal or Pillsbury are good)
- 1/4 cup (1.3 oz) rice flour
- 2/3 cup (4.8 oz) superfine sugar
- 1/4 tsp salt
- 16 tbsp (2 sticks) cold, unsalted butter
Adjust oven rack to middle position and heat oven to 425 degrees. Line an ungreased 9" round cake pan with parchment round; set aside.
In the bowl of a standing mixer fitted with a paddle attachment, mix both flours, all but 1 tablespoon sugar (reserved for sprinkling), and salt at low speed until combined, about 5 seconds.
Cut butter into 1/2" cubes with 1/4 cup of the flour mixture on a sheet of parchment paper.
Add butter and any remaining flour on parchment to the bowl with the dry ingredients.
Mix on low speed until the dough is pale yellow and resembles damp crumbs, about 4 minutes.
Remove the bowl from the mixer and toss mixture lightly with fingers to fluff and loosen; rub any remaining butter bits into the flour mixture with fingertips.
Turn half the crumbs into the prepared cake pan and even lightly with fingers. Press heavily on the mixture with a second cake pan to compress.
Add the remaining crumbs on top, even, and press down again.
Working quickly, smooth the top of the dough with the back of a spoon.
Insert a paring knife between the dough and the pan. Leaving knife stationary, rotate the pan to free the edges of the dough.
Unmold the dough onto a rimless or inverted baking sheet lined with parchment (peel the parchment round from the cake pan off top of dough, if necessary).
Place a 2" biscuit cutter in center of dough and cut out center. Place the center piece to the side, then replace the biscuit cutter into the central hole.
Place shortbread in oven and IMMEDIATELY reduce temperature to 300 degrees.
Bake for 20 minutes; remove baking sheet from oven. Score the top of the shortbread into 16 even wedges with a thin knife, then pierce all over with a skewer.
Return shortbread to the oven and continue to bake until pale golden, about 40 minutes longer.
Slide parchment onto cutting board, remove cutter from center, sprinkle shortbread evenly with reserved 1 tbsp of sugar, and cut at scored marks into wedges.
Slide parchment with shortbread onto wire rack and cool to room temperature, at least 3 hours.