In a food processor fitted with the S blade, blend the walnuts into a fine meal. Add 8 dates and process for 20-30 seconds, just until the dates are blended and combined. Press the dough into an 8" pie pan, and cover with plastic wrap and freeze until ready to use.
Add the remaining 8 dates to a small bowl and cover with water; soak for about 10-15 minutes. While the dates are soaking, prepare the apples by peeling and coring them. Cut apples into very very thin slices. When the dates have finished soaking, discard the water. Add the dates, water, cinnamon, maple syrup, vanilla and salt to a high speed blender and blend until smooth; about 15-20 seconds (this part is work!). Pour over apples and toss until the apples are evenly coated.
Remove the pie crust from the freezer. Carefully arrange apple slices into crust and press apples into crust. Freeze for about 30 minutes before serving (The freezing helps to cut the pie). Pie will keep in an air tight container for up to 6 weeks, but I doubt it will last that long.