Preheat your oven to 375°F (190°C).
Cook manicotti shells according to package instructions. Drain and set aside.
In a large bowl, mix ricotta, 1 cup mozzarella, Parmesan, egg, parsley, salt, and pepper.
Carefully stuff each shell with the cheese mixture using a spoon or piping bag.
Spread 1 cup of marinara sauce on the bottom of a baking dish.
Arrange stuffed manicotti shells over the sauce.
Top with the remaining marinara and sprinkle remaining mozzarella on top.
Cover with foil and bake for 30 minutes.
Remove foil and bake an additional 10-15 minutes until bubbly and golden.
Let it sit for 5 minutes before serving—trust me, it’s worth the wait.