In a bowl, combine the walnuts, brown sugar, egg, milk, 1 tbs of the butter, vanilla and 1/4 tsp of the lemon juice.
Line a 9" pie plate with one of the pie crusts and trim it so its even with the edge of the plate.
Spread nut mixture on top of the bottom pie crust.
In a large bowl, toss apples with remaining lemon juice.
Combine the sugar, flour, cinnamon, nutmeg and salt and toss with apples.
Spoon apples over nut mixture.
Cube remaining butter and spread out over apples.
Place the other pie crust on top and use fork to seal edges. Cut "vents" on top and brush it with some milk.
Bake at 375 for 50-60 minutes or until golden brown. (Mine usually goes for the full hour)
Let sit for about 30 minutes before serving.