Sift the ﬂour, caster sugar and rice ﬂour or semolina into a mixing bowl. Add the cubed butter and rub it in with your fingertips until the mixture clings together in heavy lumps. Gather the dough into a ball and then knead it on a lightly ﬂoured surface until smooth. Proceed according to how you wish the finished shortbread to be shaped.
Moulded Shortbread: Lightly sprinkle an 18–20cm diameter shortbread mould with ﬂour. Cut the dough in half, roll out each piece to a round a little smaller than the mould and press, smooth side down, into the mould to fit exactly. Carefully turn the dough out on a ﬂat baking tray. The mixture can also be shaped in small moulds to produce biscuit-size shortbreads.
Petticoat Tails: Cut the dough in half and roll out two rounds each 18–20 cm in diameter. Flute the edges with your fingers, then prick all over with a fork. Alternatively, fit the rounds into two ﬂuted ﬂan tins and prick well.
Shortbread Fingers: Press the dough into a shallow, 28 x 18cm tin, smooth with a palette knife, then prick well with a fork.
Having prepared the dough according to the shape chosen, chill it in the refrigerator for 1 hour and preheat the oven to 160 degrees C. Bake the moulded shortbread and petticoat tails for 20–25 minutes and fingers for 25–30 minutes, or until cooked through, but not browned.
Remove from the oven and leave to cool and firm up for 5 minutes. Loosen the moulded shortbread and petticoat tails from the baking trays with a palette knife. Mark the petticoat tails into triangles. Cut fingers into 20 equal pieces while still in the tin. Sprinkle generously with caster sugar.
After 15 minutes, transfer the petticoat tails and moulded shortbread to wire racks to cool completely. Leave the shortbread fingers in the tin until cold.
The shortbread will keep well if stored in an airtight container.