Preheat oven to 375°F (190°C).
Cook jumbo pasta shells according to package instructions until al dente. Drain and set aside to cool.
In a mixing bowl, combine ricotta cheese, shredded mozzarella cheese, grated parmesan cheese, beaten egg, minced garlic, chopped fresh parsley, salt, and black pepper. Mix until well blended.
Fill each cooked shell with the cheese mixture.
Spread a thin layer of marinara sauce on the bottom of a baking dish.
Arrange the stuffed shells in a single layer in the dish.
Spoon marinara sauce evenly over the shells.
Sprinkle additional mozzarella and parmesan cheese on top if desired.
Bake uncovered for 30-35 minutes, until the cheese is melted, bubbly, and slightly browned.
Remove from oven and let rest for 5 minutes before serving.
Garnish with extra chopped parsley and serve on a round white ceramic plate.