Cook pasta according to package directions; drain. Rinse with cold water. Drain and set aside. Meanwhile, in a small saucepan cook carrot and green onion in a small amount of water until tender; drain.

For filling, in a medium mixing bowl mash tofu with a fork. Stir in carrot mixture, ricotta cheese, cheddar cheese, 1/4 cup of the mozzarella cheese, the egg white, salt, and pepper. Set aside.

For sauce, in a medium saucepan combine undrained tomatoes, tomato paste, basil, oregano, sugar, garlic powder, and, if desired, fennel seed. 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 a 350 degree F oven about 25 minutes or until heated through. Sprinkle with remaining mozzarella cheese. If desired, serve with Parmesan cheese. Makes 4 servings.

Prepare stuffed shells but do not bake. Cover and chill up to 24 hours. To heat, bake, covered, in a 350 degree F oven for 45 to 50 minutes or until heated through. Serve as above.