As it turns out, loading all of the cheesy supreme pizza goodness into a flaky crust makes for one supremely delicious pot pie.
Place oven rack on bottom third of oven, and preheat to 425°F. Heat a large skillet over medium-high. Add sausage, and cook, stirring often, until crumbled and browned, about 6 minutes. Transfer to a bowl; set aside.
Add onion and bell pepper to skillet over medium-high. Cook, stirring often, until tender and blistered, about 6minutes. Add garlic, and cook until fragrant, about 1 minute. Stir in marinara sauce, pepperoni, olives, and cooked sausage. Remove from heat, and let cool slightly, about 15 minutes.
Press 1 piecrust in a 9-inch pie plate, allowing excess to hang over the sides. Spoon 2 cups of the sausage mixture into piecrust. Top with 1 cup of the mozzarella, and 4 slices of the provolone. Repeat with remaining sausage mixture, mozzarella, and provolone.
Place second piecrust over top, curling over and encasing top edges of bottom crust. Crimp edges, and cut 3 slits in top crust. Brush with egg. Bake in preheated oven on lower rack until golden brown, about 20 minutes. Cover with aluminum foil; continue to bake until bottom crust is golden brown, about 10 more minutes. Let stand 15 minutes before slicing.