1. Walnut Crust: Mix all ingredients together and set aside. This mixture can be made several days in advance and left at room temperature until needed.
2. Pastry Crust: Combine flour and salt. Add butter and quickly cut into flour mixture until it is the size of peas. DO NOT over mix or dough will be tough. Add just enough cold water to hold the dough together without it being wet. Wrap in plastic and set aside in the refrigerator until needed.
3. Apple Filling: Combine sugar, cinnamon, nutmeg and cornstarch and mix well. Pour over sliced apples and mix well. Set aside.
4. To Assemble: Line a 9-inch deep pie tin with parchment paper, allowing enough paper to drape over the edges by at least one inch. Place the Walnut Crust in the bottom of the lined pan and pack down tightly allowing the mixture to go about 1/2 way up the sides of the pie tin.
Take half of the pastry dough and roll out into a circle, no more than 1/4-inch thick. Place dough gently on top of the walnut mixture.
Fill the pie with the prepared apples and arrange the tablespoon of butter pieces all over the top.
Roll out the other half of the pastry dough and place over the top of the pie. Brush cold water between the top and bottom crusts so that the dough will seal together. Trim away the extra dough allowing enough to pinch together into a decorative pattern. Pierce the top crust in several places to allow steam to escape.
Bake at 325 degrees for 60 to 70 minutes or until the crust is a deep golden brown and the apples have begun to bubble and the juices are running. Remove from the oven and cool to room temperature.
Once the pie is completely cold (at least 6 to 8 hours), invert it into either another pie tin or onto a platter, then gently peel away the parchment paper.
Cut into the desired number of pieces and serve either at room temperature or reheat at 350 degrees for 10 minutes.
Bake this pie on a cookie sheet so that if any of the bubbling juices run over the edges, they will not burn on the bottom of your oven.
Serve this pie warm, with cinnamon ice cream and drizzled with caramel sauce, homemade or store-bought.
If you are running short on time, you can always use a purchased frozen unbaked apple pie. Remove the frozen pie from the tin, line with parchment paper and add the walnut mixture. Place the frozen pie on top of the walnuts and bake as indicated above. This is a great way to add a homemade touch to a pre-bought pie.