Place the flour in a large glass bowl and add the salt, then disperse the cubed butter over it.
Firmly grab and squeeze handfuls of flour and butter to start mixing them together.
Rub the flour and butter between your fingertips to remove any lumps.
Work fast to avoid warming the mixture, and you should end up with a coarse and sandy mixture with a minimum of lumps.
In a small bowl, combine the egg, water, salt and sugar (if using) then beat with a fork to get a smooth mixture.
Make a well in the flour and butter mixture.
Pour the egg mixture into the well and use a wooden spoon to incorporate the liquid into the flour.
When the liquid has been absorbed and as soon as clumps of dough start to form, knead gently until you can gather the dough into a ball when pressed in your palm.
Gather the dough into a rough ball shape and transfer it to your kitchen countertop.
Dust your kitchen counter with a pinch or two of flour and flatten the dough into a thick disk (avoid overworking the dough).
Wrap in plastic film and rest in the fridge for at least an hour (two hours is best) to firm up.
If resting for 2 hours or more, remove the shortcrust from the fridge at least 20 minutes before using it in a recipe.
