Preheat oven to 350 degrees F
Brown the Italian sausage so there is no longer any pink. Drain any excess grease. Set aside.
In a medium bowl combine the cottage cheese, 1/2 of the mozzarella, Parmesan cheese, egg, and Italian seasoning. Mix until well combined. Add 1/2 of the Italian sausage and mix well.
Cook the manicotti noodles using the instructions on the box. Drain and cool so they are easy to handle.
Mix the remaining Italian sausage with the spaghetti sauce. Spread 1 1/2 cups of the meat/spaghetti sauce in a 9 by 13-inch baking dish.
Divide the cheese sauce between the 12 manicotti noodles (about 1/3 cup per noodle). Place the filled noodles on top of the meat sauce in the baking dish.
Pour the remaining meat sauce over top of the filled noodles. Cover with aluminum foil and bake in the preheated oven for 25 minutes.
Remove the manicotti from the oven. Remove the aluminum foil from the pan and top with the remain mozzarella cheese. Bake uncovered for 15 more minutes or until the mozzarella is melted.
Remove from the oven and let it rest for about 5 minutes and serve.