In a bowl cream 4 sticks (2 cups) unsalted butter, softened. Beat in 1 cup sugar and beat mixture until it is light and fluffy. Stir in 4 cups and 1 tablespoon all purpose flour and 1/4 teaspoon salt and knead the dough briefly on a floured surface with floured hands. The dough will be soft. Press the dough into a 9"x13"x2" baking pan, prick with fork at 1/2" intervals and bake in a preheated 275 degree oven for 1 1/2 hours or until pale golden. Turn off oven and cut shortbread into 1" squares. Return shortbread to oven and let it cool completely. Makes 117 squares.