In a bowl, combine flour and salt; cut in shortening.
Gradually add cold water, 1 tablespoon at a time, tossing lightly with a fork until dough forms a ball.
Chill for 30 minutes.
On a floured surface, roll half of dough into a 10-in.circle.
Place into a 9-in.pie pan.
In a bowl, toss apples with lemon juice.
Combine sugar, flour, cinnamon, salt and nutmeg; add to apples and toss.
Pour into crust; dot with butter.
Roll out remaining pastry to fit top of pie; cut slits in top.
Place overfilling; seal and flute edges.
Beat egg yolk and water; brush over pastry.
Bake at 425° for 15 minutes.
Reduce heat to 350°; bake 40-45 minutes more or until crust is golden and filling is bubbly.