1. For the pie crust: Process the flour, salt and sugar in a food processor until combined. Add the shortening or butter and process until the mixture has the texture of coarse sand, about 10 seconds. Scatter the butter pieces over the flour mixture; cut the butter into the flour until the mixture is pale yellow and resembles coarse crumbs, with butter bits no larger than small peas, about ten 1-second pulses. Sprinkle 4 tablespoons of the ice water over the mixture. Continue to pulse until the mixture comes together in a loose ball. Flatten the dough into a disk, wrap in plastic and refrigerate for at least 1 hour, or up to 2 days.
Note: If you do not have a food processor, use this method to make the pie dough: In a large bowl, whisk together the flour, sugar and salt. Scatter the shortening and butter over the dry ingredients and, using a pastry blender or your fingers, work the fat into the flour mixture until it looks like coarse sand. Then sprinkle the water over the mixture and use a fork to incorporate until it is evenly moistened and the dough will hold together when pinched between your fingers.
2. Remove the dough from the refrigerator. Roll the dough on a lightly floured work surface to a 12-inch circle. Transfer the dough to a 9-inch pie plate. Ease the dough into the pan corners. Trim the dough edges to extend about ½ inch beyond the rim of the pan. Fold the overhang under itself; flute the dough or press the tines of a fork against the dough to flatten it against the rim of the pie plate. Refrigerate the dough-lined pie plate until firm, about 40 minutes, then freeze until very cold, about 20 minutes.
3. Adjust an oven rack to the lower-middle position and hat the oven to 375 degrees F. Remove the dough-lined pie plate from the freeze, press a doubled 12-inch piece of heavy-duty foil inside the pie shell, and fold the edges of the foil to shield the fluted edge; distribute 2 cups ceramic or metal pie weights over the foil. Bake, leaving the foil and weights in place until the dough looks dry and is light in color, 25 to 30 minutes. Carefully remove the foil and weights. Continue baking until deep golden brown, about 12 minutes more. Transfer to a wire rack and increase the oven temperature to 425 degrees F.
4. For the apple filling: Peel, quarter, and core the apples; slice each quarter crosswise into pieces ¼ inch thick. Toss the apples, sugar, cinnamon, and salt in a large bowl to combine. Heat the butter in a large Dutch oven (or pot) over high heat until foaming subsides; add the apples and toss to coat. Reduce the hat to medium-high and cook, covered, stirring occasionally, until the Granny Smith apple slices are tender and the McIntosh apple slices are softened and beginning to break down, about 10 minutes.
5. Set a large colander over a large bowl; transfer the cooked apples to the colander. Shake the colander and toss the apples to drain off as much juice as possible. Bring the drained juice and the cram to a boil in the now-empty Dutch oven over high heat; cook, stirring occasionally, until thickened and a wooden spoon leaves a trail in the mixture, about 5 minutes. Transfer the apples to the prebaked pie shell; pour the reduced juice mixture over and smooth with a rubber spatula.
6. For the streusel topping: Combine the flour and sugars in a medium bowl; drizzle with the melted butter and toss with a fork until evenly moistened and the mixture forms many large chunks with pea-sized pieces mixed throughout. Sprinkle the streusel evenly over the pie filling. Set the pie plate on a baking sheet and bake until the streusel topping is deep golden brown, 10 to 20 minutes. Cool on a wire rack to room temperature and serve.