Mix the butter and sugar together (preferably with a wooden spoon) until it is pale and creamy. Sieve both the flour and the cornflour into the bowl and mix well. Put a small amount of flour on your working surface and place the dough on this. Shake a little flour on top and roll out about quarter inch thick. Prick with a fork and cut into rounds with a cutter or, if you want one large shortbread round, pinch the edges with thumb and finger all round.

Use a palette knife to lift the shortbread onto an oiled baking tray and bake for 25 minutes in a pre-heated oven at 325F/170C/Gas Mark 3. If the biscuits are ready, they will be pale brown and crisp; if not, return to the oven for 5 or 10 minutes. Shake a small amount of caster/granulated sugar on the top of the shortbread immediately after they have been removed from the oven. Use a palette knife to move them to a cooling rack and store in an airtight tin once they are cold.