To make the crust, cook the spaghetti "al dente" according to the package directions. Drain well and return to the pot. Add the Parmesan cheese and toss to mix well. Add the egg and toss again. Coat a 10-inch pie pan with nonstick cooking spray and spread the mixture evenly over the bottom and up the sides of the pan. Set aside.
To make the sauce, coat a large nonstick skillet with cooking spray and preheat over medium heat. Add the ground beef and cook, stirring to crumble, until the meat is no longer pink. Drain off any excess fat. Add the mushrooms, onions, and Italian seasoning or oregano. Cover and cook for about 4 minutes more or until the onion starts to soften. Add the undrained tomatoes and the tomato paste, cover and cook over medium low heat for 5 minutes more, stirring occasionally, until the flavors are blended. Remove the skillet from the heat and set aside.
To assemble the pie, spread the ricotta cheese over the bottom of the crust, then cover the ricotta layer with the sauce. Spray the exposed edges of the crust (if any) lightly with the cooking spray, and bake uncovered at 350°F for 25 minutes, or until heated through. Spread the mozzarella over the top of the sauce, and bake for 5 minutes more or until the cheese is melted. Remove the pie from the oven and let sit for 10 minutes before cutting it into wedges and serving.
Cover pie pan with foil; label and freeze.
To Serve from Freezer:.
Thaw. Bake, covered for 25 min at 350. Remove foil and bake for 5 more minutes.