To make the pastry, tip the flour onto the bench and make a well in the centre. Dice the butter and put it and the salt into the well, then use a pastry scraper to cut the butter into the flour. Make a well again and pour in the cold water. Using the pastry scraper work in the flour and butter into the water, do not knead the dough.
At this point the dough will look very lumpy (the butter still in pieces), but it should hold together.
Flour your working bench, Roll out the pastry to make a rectangle about 1.5cm thick. Keeping the longer side of the rectangle parallel to the bench, fold both ends into the centre – it will look like an open book. Then fold one side over the other – to close the book. Cover and place pastry in the fridge for 20 minutes.
Repeat this step twice. Any leftover pastry can be wrapped and frozen.