1) To make the crust: Whisk together the flour and salt, then work in the shortening until everything is well combined.
2) Work in the butter until the mixture is unevenly crumbly; some pieces of butter can be left a bit larger than the others.
3) Add the water 1 tablespoon at a time, mixing as you sprinkle the water onto the flour/fat.
4) When the dough is moist enough to hold together when you squeeze it, transfer it to a lightly floured work surface. Knead the dough three or four times to bring it together, then pat it into a thick disk. Roll the disk on its edge, like a wheel, to smooth out the edges. This step will ensure your dough will roll out evenly, without a lot of cracks and splits at the edges later. Wrap in plastic and refrigerate for 30 minutes, while you make the filling.
5) To make the filling: Put the sliced apples in a big microwave-safe bowl, and stir in the brown sugar, cinnamon, salt, nutmeg, lemon juice, and boiled cider.
6) Microwave the filling, uncovered, for 5 minutes. This softens the apples just a bit, and gets their juices flowing. Skip this step if you like; it's not critical, though we think it helps.
7) Stir in the flour or Pie Filling Enhancer.
8) Preheat the oven to 425°F.
9) Remove the crust from the refrigerator. If it's been chilling longer than 30 minutes, give it 10 minutes or so to warm up a bit. Roll it into a 12 1/2" to 13" circle.
10) Lightly grease a 9" pie pan, preferably one that's at least 1 1/2" deep, and lay the crust in the pan, settling it into place gently. Don't tug at it or stretch it; this could cause it to shrink as it bakes.
11) Spoon the filling into the crust.
11) To make the topping: Combine the sugar, flour, and butter, working them together until crumbly. Don't over-mix; you don't want the streusel to turn into a solid mass.
13) Spread the streusel atop the filling.
14) Place the pie in a brown paper grocery bag. If you're nervous about baking in a paper bag, see our tip about baking in parchment, above. Secure the bag closed; staples or uncoated paper clips work well for a paper bag. Place the pie in its bag on a baking sheet, which will make it easier to handle.
15) Bake the pie for 1 hour.
16) Remove the pie from the oven, and carefully open it, avoiding any steam. Remove the pie, and set it on a rack to cool for at least 30 minutes before slicing.
Yield: one 9" pie, 8 to 10 servings.