Ricotta Stuffed Shells

This is a standard favorite...you could do it without the ground beef but my husband is a meat eater so gotta have it there.

20 pasta shells, cooked
1 jar spaghetti sauce
1 lb ground beef
2 cups shredded mozzarella cheese, divided
1 small container ricotta
1/2 cup grated Parmesan cheese
1 egg

Cook ground beef until brown. Once brown, drain and return to pan. Add spaghetti sauce and cook on low until warm. Meanwhile, mix 1 cup mozzarella cheese, ricotta cheese, Parmesan cheese and egg in a large bowl. Pour a small amount of spaghetti sauce in bottom of a casserole dish to keep them from sticking. Stuff cooked pasta shells with a large spoonful of cheese mixture and place seam side down in the dish. Pour beef sauce over top of the stuffed shells and make sure all are throughly covered with sauce. Sprinkle remaining cup of mozzarella cheese over the top of the dish. Cover with foil and cook at 350 degrees for 25 mins.