Cook pasta 80% done. Stir constantly to prevent noodles from burning. Brown meat, drain. Cook sausage 80% done, cool and chop into small chunks. Mix hamburger, pork, sausage, ziti, sauce, diced onion and seasoning into large skillet. Cook on low for 10-15 minutes. Meanwhile mix ricotta cheese and egg in mixing bowl, stirring for consistency. Mix in one cup mozzarella cheese. Using 9x13x3 BROILING PAN, not a baking pan, pour 1 inch of meat mixture into pan. Layer mozzarella cheese mixture. Sprinkle parmesan cheese over mixture. Add another layer of meat mixture. Top this with mozzarella cheese and parmesan on top of that. This will be about 2/3 of ingredients, cook remaining mixture in casserole dish. Turn top of broiler pan upside down (keeps foil from sticking to food) and cover with foil. This allows more even cooking and you can finish baking by removing cover more easily. Cook at 250 degrees for one hour fifteen minutes or until cheese is melted and center is hot. Center of mixture should be bubbling, not just outside edges. Uncover pan and cook uncovered for 10 more minutes.