Mix together and let stand. Mix 2 1/2 cups flour and 1 teaspoon salt. Cut in 1/2 cup shortening and 1/2 cup butter. Beat 1 egg yolk in measuring cup and add enough milk to make 2/3 cup. Add to flour mixture. Take 1/2 of dough and press into large cookie sheet. Spread apples on dough. Roll rest of dough and place on top. Seal edges and cut slits in top. Beat egg white until frothy and brush on top. Bake at 375 degrees for 50 minutes.
Combine 1 cup powdered sugar and 3 to 4 tablespoons milk, and drizzle on while warm.
