PASTRY: Sift together flour and salt. With a pastry blender or two knives cut in shortening.
Separate egg, putting egg yolk in measuring cup. Add milk to measure 2/3 cup.
Slowly mix in to the flour mixture, do not ovemix. Divide pastry in half.
Put first half of pastry on a cookie sheet. Sprinkle 1 cup cornflakes over pastry, then spread apple mixture over first layer of pastry, leaving an inch around the edges. Put second layer over top, Press together around the edges.
Beat egg white and spread over top of pastry.
Cook in moderate oven (350F) until tender, about 15-20 minutes. Cool slightly.
ICING: Add enough water to make a paste. Drizzle over top.