How to Make It
In a food processor, pulse the flour and salt. Add the butter and pulse 10 times. Sprinkle on 1/2 cup plus 1 tablespoon of the ice water and pulse 5 times. Add another 1/2 cup of the water and pulse 5 times, until the dough just holds together when pinched; add the remaining 1 tablespoon of water if necessary. Divide the dough into thirds. Form 2 pieces into 8-inch disks. Cut the remaining dough in half and form into 2 small disks. Wrap all the disks in plastic and refrigerate until firm, at least 1 hour.
In a saucepan, cook the bacon until crisp. Transfer the bacon to a plate and pour off the fat.
Add 2 tablespoons of the oil and the onion to the pan and cook over moderate heat until the onion softens. Add the garlic and herbs; season with salt and pepper. Add the tomatoes with their juice; crush with a potato masher. Cook, stirring occasionally, until the sauce is very thick, about 30 minutes.
Bring 2 cups of water to a boil. Add the porcini and let stand until softened, 10 minutes. Drain, reserving 1 cup of the soaking liquid. Rinse and finely chop the porcini.
In a large, deep skillet, heat 1/4 cup of the olive oil. Add the porcini and cremini and cook over moderately high heat until the cremini are lightly browned, 7 minutes. Add the mushrooms and the bacon to the tomato sauce.
Add the ground beef and sausage to the skillet, season with salt and pepper and cook over high heat, breaking up the meat, until lightly browned, 15 minutes. Spoon off as much fat as possible. Add the wine and cook until evaporated. Add the demiglace and the reserved 1 cup of porcini soaking liquid and simmer over moderate heat for 15 minutes. Add the meat to the tomato sauce and simmer until nearly dry, about 10 minutes.
Preheat the oven to 350°. On a lightly floured surface, roll out each large piece of the dough into an 18-inch round. Fit the dough into two 10-inch springform pans (2 1/2 to 3 inches deep), allowing it to hang over the rims. Line the dough with parchment and fill with pie weights. Refrigerate until firm, at least 10 minutes. Bake the crusts for 30 minutes; remove the paper and weights and bake until golden, about 15 minutes longer. Let the crusts cool slightly. Carefully trim the overhang flush with the rims. Turn the oven up to 400°.
In a large pot of salted boiling water, cook the pappardelle until al dente; drain and toss with the remaining 1 tablespoon of olive oil.
Sprinkle 1/4 cup of the Parmigiano in each crust. Top with one-fourth of the pasta, 2 1/2 cups of the sauce and one-fourth of the mozzarella. Repeat the layering, ending with the mozzarella.
On a lightly floured surface, roll the two smaller pieces of dough into 11-inch rounds. Brush the rims with the egg wash and invert the rounds over the filling; press the edges to seal and trim the dough as necessary. Brush the tops with egg wash and make several slits to release steam. Bake until the top crusts are golden and the pies are hot, 30 to 35 minutes: To test, insert a metal skewer into the centers for 5 seconds. If the skewer feels hot, the pie is ready. Let cool for 15 minutes, then unmold. Serve in wedges with the warm tomato sauce.