Mix together Ricotta, eggs, salt, pepper, Parmesan and sugar until smooth. Fill UNCOOKED manicotti noodles with this mixture. Brown beef and drain off fat. Add sauce, water and mushrooms and simmer for 10 minutes.
Grease 1 large or 2 smaller (2 1/2 quart) casserole. (I usually divided it in 2 casseroles and freeze one). Spoon a small amount of meat sauce on bottom, then layer stuffed manicotti; pour meat sauce on top, then sprinkle with grated Mozzarella. Bake at 400-425 degrees COVERED for 45 minutes, then uncover and bake for 5 more minutes. Serve immediately.
