For the Filling:

1. Peel, core, and slice the apples into a large bowl. Toss the apples with sugar, flour, spices and orange zest. Set aside.

For the Crust:

1. In the bowl of food processor, pulse together flour, salt, egg, shortening, and lemon juice until the dough holds together. Form into a disk and wrap in clingfilm. Refrigerate for 30 minutes or until ready to use.

For the Caramelized Walnut Topping:

1. Line a 9-inch pie plate with parchment paper and set aside.
2. In a small glass bowl, mix together melted butter, brown sugar, and walnut halves. Transfer the mixture to the lined pie plate and set aside.
3. Preheat oven to 350 degrees F.
4. Divide the prepared pie dough in half. On a well-floured surface, roll out one half of the dough and fit into the pie plate, over the walnut mixture. Fill with the apple mixture.
5. Roll out the remaining pie dough to place over the filling. Press the edges of the crust and primp.
6. Prick the top of the crust with a fork, brush with the egg wash and sprinkle with sugar. Place the pie on a baking sheet and bake 30-35 minutes or until nicely golden.
7. Let the pie rest for about 5 minutes before inverting onto a serving plate. Best when served warm with a little ice cream or whipped cream if desired.