Mix the flour and sugar first, and then rub in the butter.
Knead the mixture until it becomes a smooth paste.
Roll out till about 3/4 inch thick or 2cm thick.
Cut into rectangles and decorate the top with a fork creating rows of holes.
Transfer to a greased baking sheet and bake for 20-25 minutes at 160°C (325°F/Gas Mark 3). They want to stay pale and light golden.
In warm weather you may want to chill the cookies before baking.
This recipe can also be used for petticoat tails. Just split the mixture in two and flatten into 7 inch rounds about a half inch thick (1cm). Mark top into 8 portions and decorate with a fork. Bake for 30 minutes.
To use a shortbread mold: Mix a teaspoon of flour and a teaspoon of caster sugar. Grease the mold with oil and evenly sprinkle half the flour/sugar mix. Press the shortbread into the mold, and turn out onto a baking sheet before baking.