In a large bowl, combine flour and salt.
Rub in the cold butter until mixture resembles coarse breadcrumbs. You can do this by hand or you can use a dough cutter.
Mix in the egg until fully incorporated. Stir in the water a little at a time until the mixture forms a tight ball. (You might not need all of the water so add it slowly).
Divide about 3/4 of the ball and form both pieces into round discs. Wrap each one in plastic and refrigerate for 30 minutes. (Can be made 24 hours in advance if desired.)
When ready to use, roll the bigger piece of dough to fit the baking vessel you are using, roughly 1/4 inch thick. Roll the smaller piece to fit over the top, about 1/4 inch thick as well.