Make sure your butter is not too fridge hard.
Beat it together with the sugar until you have a lovely pale color.
Stir in the flour to form a smooth paste.
Roll out the pastry until it is about a centimeter thick (½ inch).
Cut into your desired shape (a circle, a finger, whatever) and, if you like, sprinkle with a little more caster sugar.
Place the cookies on a baking sheet and chill for 20 minutes.
Bake in the oven for 15-20 minutes until pale golden.
Cool before eating (if you can manage it).