Sift your flour and salt into a large bowl, also adding your butter. Work the butter delicately through the flour and salt with your fingertips. Lifting it up allowing the air to get into it, you want to achieve a light crumb consistency. Now add the caster sugar, gently sifting through the mixture with your fingertips. Gradually add your beaten egg, mixing in with a fork. We also added a tbsp of chilled water, you want all the ingredients to come together into a smooth pastry, (add slightly more water if needed). Use your hands to bring this together into a ball, wrap in clingfilm and chuck into the fridge for 30 minutes to chill.