Mix flour and salt. Cut margarine in. Whisk egg yolk and milk together; mix into flour. Roll out 1/2 of dough large enough to fit into a jelly roll pan.
Sprinkle corn flakes over bottom crust. Spread apple slices evenly over crust. Mix sugar, cinnamon and salt; sprinkle over apples. Roll out remaining dough and cover fruit. Brush top with beaten egg white. Bake at 350°F for about 1 hour, until crust is golden brown.
Mix glaze ingredients together well. Brush on top crust while still hot.