In a bowl, combine flour and salt; cut in shortening until mixture resembles coarse crumbs. Combine egg yolk and milk; add to flour mixture. Stir just until dough clings together. Divide dough in half.
On a lightly floured surface, roll half of dough into a 15x10-in. rectangle; transfer to a greased 15x10x1-in. baking pan. Set aside.
In a bowl, toss together filling ingredients; spoon over pastry in pan. Roll out remaining dough into another 15x10-in. rectangle. Place over filling. Brush with egg white. Bake at 375° for 40 minutes or until golden brown. Cool on a wire rack.
For glaze, combine the confectioners' sugar and enough water to achieve a drizzling consistency. Drizzle over warm pastry. Cut into squares. Serve warm or cold.