In a large bowl, stir together the flour and salt.
Cut in the butter to pea sized chunks.
Place the egg and vinegar in a measuring cup and add cold water to measure 1/2 cup of total liquid.
Pour this into the flour mixture and mix just until the dough can be made into a large ball.
Divide dough into four equal portions. Wrap in plastic and store in the refrigerator. Dough may be refrigerated for up to three days or frozen for up to three months.
