Scottish cooking authority Catherine Brown provided us with this recipe. Rice flour yields crisper shortbread, while that made with cornstarch is softer.
- 2 cups cake flour
- 1⁄4 cup rice flour or cornstarch
- 8 oz. butter, cut into pieces
- 9 tbsp. plus 1/2 tsp. superfine sugar
Sift cake flour and rice flour or cornstarch together onto a clean surface. Knead butter and 9 tbsp. of the sugar together on same surface, working quickly so as not to soften the butter too much with the heat of your hands. Gradually work flour mixture into butter mixture, kneading until a rough dough forms. Scrape up scraps of dough (including any dough stuck to your hands) with a spatula or a dough scraper and add to dough ball. Give dough several quick kneads to form a smooth ball.
Divide dough into thirds and shape each into a 1⁄4"-thick 6" disk. Using the spatula or dough scraper, carefully transfer disks to a large parchment-lined baking sheet at least 1" apart. Prick disks all over with a fork, then press with tines to mark circumference of top outer edge. Transfer to the refrigerator to let chill for 1 hour.
Preheat oven to 300°. Bake shortbread until pale golden, 30-40 minutes, dusting cakes with remaining sugar 10 minutes before finished baking. Score each cake into 6 wedges while still warm, then allow to cool completely.