In a medium bowl, combine the flour, sugar and 1/2 tsp. salt. Using a pastry blender, a fork or your fingers, incorporate the butter and shortening into the flour mixture until it resembles coarse crumbs. Gradually sprinkle 1/2 cup ice water over the flour mixture, tossing until large, moist clumps form. Press the dough into a ball, and work it with your hands until it just comes together. (Don't worry if the dough seems slightly dry. As it rests, the flour will continue to absorb liquid. Don't add any extra liquid, or your crust won't be flaky.)
Divide the dough in half, shape each piece into a ball, then flatten each ball into a disk and wrap in plastic. Chill the dough at least 20 minutes or up to overnight before rolling.
Position a rack in the center of the oven and preheat to 475 degrees. On a lightly floured surface, roll out one dough disk to a 12-inch round. Transfer it to a 9-inch deep-dish pie pan, gently fitting it into the pan. Roll out the other dough disk; transfer to a parchment paper-lined baking sheet. Refrigerate the crusts until ready to use.
In a large bowl, toss the apples with the lemon juice. In a small bowl, mix 3/4 cup sugar, the flour, cinnamon, nutmeg, allspice and 1/4 tsp. salt; sprinkle over the apples and toss until well combined. Transfer the apples to the pie pan. Dot the top with the butter. Cover with the top pastry, trim the overhang and, using your fingers or a fork, crimp the edges to seal.
In a small bowl, whisk the egg yolk and cream. Cut 4 slits in the top crust, brush with the egg mixture and sprinkle with the remaining 2 tbsp. sugar. Set the pie on a parchment-lined rimmed baking sheet to catch any drips.
Place the pie in the oven and reduce the temperature to 425 degrees. Bake 15 minutes. Rotate the pie pan and reduce the oven temperature to 350 degrees. Bake until the crust is nicely browned and the juices are bubbling, tenting with foil if browning too quickly, 45 to 50 minutes more. Let cool on a wire rack at least 4 hours before serving.