Cook the pasta shells according to the directions on the box, drain. Rinse with cold water, drain and set aside.
Meanwhile in a small saucepan cook carrot, zuchinni, and onion in a small amount of water until tender; drain.
For the filling, in a medium mixing bowl mash tofu with a fork. Stir in carrot mixture, monterey cheese, 1/2 cup of the mozzarella, salt and pepper. If you're choosing to use the ricotta and egg white add them now. Set aside.
For the sauce, in a medium saucepan combine undrained diced tomatoes, tomato paste, basil, oregano, garlic, and garlic powder. Bring to a boil; reduce heat. Simmer, uncovered, for 10 minutes.
Stuff each cooked pasta shell with about 1 rounded tablespoon of the filling. Place shells in an ungreased 2 quart square baking dish. Pour sauce over shells.
Cover and bake in in 350 degree oven about 25 minutes or until heated through. Sprinkle with remaining 1/2 cup mozzarella cheese. If desired, serve with Parmesan cheese.