Combine the flour and salt in a mixing bowl. Using your hands work the butter and shortening into the flour, until the mixture resembles coarse crumbs. Sprinkle the ice water over the mixture 1 or 2 tablespoons at a time. Gather the dough into a ball. Turn the dough onto a floured surface. Using the heel of your hand knead the dough, this will blend the butter and shortening and make the pastry flakier. Refrigerate for 30 minutes. Roll the dough out onto a floured surface into a circle 14-inches in diameter and 1/8-inch thick. Gently fold the circle of dough in half and then in half again so that you can lift it without tearing it, and unfold into a 9-inch tart pan.