Boil the manicotti shells in salted water according to package instructions until tender. Drain carefully and let them cool so they do not tear while filling.

In a mixing bowl, combine ricotta cheese, 1 cup mozzarella, parmesan cheese, egg, garlic powder, Italian seasoning, salt, pepper, and parsley. Mix until smooth and creamy.

Use a spoon or piping bag to gently fill each manicotti shell with the cheese mixture without breaking the pasta.

Spread 1 cup of marinara sauce in the bottom of a baking dish. Place filled manicotti shells on top and cover with remaining marinara sauce.

Sprinkle the remaining mozzarella cheese over the top. Cover with foil and bake at 375°F for 25 minutes.

Remove foil and bake for another 10 minutes until cheese melts and becomes slightly golden. Let rest for 5 minutes before serving.