Preheat oven to 375 degrees F.
Spread 1 cup of marinara evenly in a 9"x13" baking dish.
In a bowl, mix the ricotta, 1 1/2 cups of mozzarella, 1/2 cup of parmesan, Italian seasoning, red pepper flakes, egg, salt, pepper, and parmesan.
Fill each shell with the cheese mixture and place in the dish.
Pour the rest of the marinara over the top of the shells and sprinkle with remaining mozzarella and parmesan.
Cover with foil and bake for 20 minutes. Remove the foil and bake for another 10 minutes or until the cheese is melted.
Sprinkle parsley over the top and enjoy!