Mix flour and salt, cut in shortening. Combine milk and egg yolk; add to flour mixture. Roll out half of the mixture on floured surface to fit 11 x 16 x 1/2 inch jelly roll pan. Place in pan.
Arrange apples on crust. Combine sugar, flour and cinnamon. Sprinkle over apples. Dot with butter. Roll out remaining pastry and place over apples. Brush pastry with egg white. Bake at 375 for 45 minutes.