Traditional Shortbread

I love to bake and most of the time it works out ok. But there has been one thing I have not been able to get the hang of.....until now.
Last night my friend Judith sent me an old family recipe for traditional shortbread and of course I had to try it out. The below measures are imperial, but I think it will work with any quantities as long as the 1, 2, 3 method is used: 1 measure of sugar, 2 measures of butter, 3 measures of plain flour.

Ingredients:

4oz caster sugar (+ a bit extra for sprinkling on the top)
8 oz butter
12 oz flour

Method:

Preheat the oven to 170C (fan oven 160C)/325F
Cream together sugar and butter.
Put this in the fridge for about half an hour so the butter is nice and cold before rubbing in the flour until the mixture resembles bread crumbs.
Add about a tablespoon of liquid to help it combine together and spread out onto a baking tray.
Prick all over with a fork and sprinkle with the sugar.
Bake in the oven for about 30 minutes until cooked but hardly coloured.
Cut into squares or fingers and enjoy with a nice cup of tea