1. First make the crust: In a medium bowl, whisk together the flour, sage, and salt until well combined. Sprinkle the butter cubes over the flour mixture and use your fingers to work them in (you want to rub your thumb against your fingertips, smearing the butter as you do so). Do this until the mixture looks like cornmeal with some pea-sized bits of butter remaining. Stir in the cheese with a fork until evenly distributed. Sprinkle 6 tablespoons ice water over the mixture and stir with a fork until the dough begins to come together. If needed, add an additional tablespoon or two of ice water (you shouldn`t need much more). Turn the dough out onto a lightly floured surface and knead three times. Gather the dough into a ball, then divide into two portions, making one slightly bigger than the other. Press each portion down into a disk and wrap in plastic wrap. Refrigerate for at least 30 minutes. 2. Make the filling: In a skillet over medium-low heat, cook the apples without any oil, stirring gently, until they just begin to soften, 5 to 7 minutes. Transfer to a dish and set aside. Add oil to the pan and increase the heat to medium-high. Add the onion, pork, brown sugar, salt, and spices. Cook, using a wooden spoon to break up the meat, until it is lightly browned, about 10 minutes. Let the meat mixture cool for 10 minutes, then transfer to a food processor. Add the breadcrumbs and pulse five times until the mixture has the texture of coarse sand. Set aside. 3. Prepare the crust: Unwrap the larger disk of dough and put it in the center of a large sheet of parchment paper or wax paper. Cover the dough with a second piece of parchment. Roll out, working from the center, to a 13-inch circle. Peel off the top piece of parchment and transfer the dough to a pie plate, peeled side down. Peel off the remaining parchment and press the crust into the sides of the pie plate, draping any excess over the edge. Unwrap the smaller disk of dough and put it in the center of a large sheet of parchment paper. Cover the dough with a second piece of parchment. Roll out, working from the center, to an 11-inch circle. Set aside. 4. Preheat the oven to 425°F and set a rack to the second-to-bottom position. Fill the pie: Pour the meat mixture into the bottom crust and gently smooth the top with a spatula. Arrange the cooked apple slices over the meat, pressing down to make the whole construction as smooth and neat as possible. Peel the top sheet of parchment off the top crust. Transfer, peeled side down, to the pie, then peel off the remaining parchment. Using a sharp knife, make two 3-inch slashes in the crust to allow steam to escape. Fold the edges of the bottom crust up over the top crust and crimp the edges to seal. Brush the crust with the egg wash and decorate with sage leaves, if desired. Bake at 425°F for 10 minutes, then reduce the heat to 375°F and bake until the crust is golden brown, 25 to 35 minutes more. Remove from oven and let cool 25 minutes before serving.