This pastry dough calls for pastry flour, a special flour that you may not already have in your pantry, but the results are well worth acquiring it for a crust that's both flaky and tender. We prefer unbleached pastry flour, such as King Arthur. If you prefer, you can substitute cake flour for the pastry flour. The pastry or cake flour keeps the pastry dough tender, and the vinegar strengthens the gluten and adds elasticity. This pastry dough has more salt than most. Kosher salt is coarser than table salt. If you are using table salt instead, cut the amount of salt in half.