Ingredients
175g plain flour, plus extra for dusting 
115g butter 
50g of caster sugar, plus a little extra for sprinkling 

Method

Put the flour and butter into a mixing bowl and rub the together until the mixture looks like breadcrumbs.  Stir through the sugar and push and squeeze the mixture to bring together as a dough. It might look initially too crumbly but it is a very buttery recipe so it will work, just be firm and patient. Bring into a ball and wrap in cling film and put into the fridge for 30 minutes. 

After 15 minutes preheat the oven to 170c. 

Line a baking tray and roll out the dough to a circle with a rolling pin if you like - you can also push the dough down with your hands to shape, I like the rustic look of this so this is what I do but either works well.

With a blunt knife, run it through the middle of the dough gently score, turn 90 degrees and again run your knife gently through the middle so you have a cross, turn 45 degrees and repeat to make another cross.  This should give you 8 pieces of shortbread. 

Cook in the oven for 15-20 minutes until golden.  Remove from the oven and whilst still hot, take a knife and cut through your lines so you have individual biscuits.