Preheat oven to 350 degrees.
Brown Italian sausage and ground beef together with onion. Drain and add spaghetti sauce. Turn heat down to low and let simmer.
Cook spaghetti according to package. While spaghetti is cooking, mix together the butter, parmesan cheese and eggs.
Drain spaghetti and mix in the cheese/butter/egg mixture.
Spread a little sauce on the bottom of a 9″x13″ and top with half of the spaghetti noodle mixture. Spread half of the cottage cheese over top of the noodles and then half of the sauce over that. Sprinkle on half of your mozzarella cheese and then repeat the layers, leaving the other half of the mozzarella aside.
Cover with foil and bake for 40 minutes.
Remove foil, sprinkle on the remaining mozzarella cheese and bake again until the cheese melts, about 10-15 minutes.
Serve and enjoy!