Combine flour, salt, shortening, egg yolk, and milk.

Mix until a pie crust consistency is achieved.

Divide the pastry into two equal portions.

Roll out one portion of the pastry to fit a 10 1/2 x 15 1/2-inch tray.

Line the tray with the rolled-out pastry.

Sprinkle corn flakes evenly over the pastry base.

Slice the apples into thin pieces.

Spread the apple slices over the corn flake-covered pastry.

In a separate bowl, mix sugar and cinnamon.

Sprinkle the sugar and cinnamon mixture evenly over the apple slices.

Roll out the remaining pastry portion.

Carefully place the second layer of pastry over the apple filling.

In a small bowl, whisk together the egg white and water.

Brush the egg white and water mixture over the top pastry layer.

Bake in a preheated oven at 400°F (200°C) until golden brown, approximately 35-40 minutes.

Let cool completely.

Prepare a powdered sugar frosting.

Frost the cooled apple bars with the powdered sugar frosting.

Cut into bars and serve.