Preheat your oven to 375°F (190°C).
Cook the pasta shells according to package instructions until al dente, then drain and rinse under cold water.
In a large bowl, combine ricotta cheese, half of the mozzarella, Parmesan, beaten egg, garlic powder, herbs, salt, and pepper.
Spoon the cheese mixture into each pasta shell; place the filled shells into a baking dish.
Spread half of the marinara sauce over the stuffed shells, covering them evenly.
Sprinkle the remaining mozzarella cheese over the shells, then drizzle with the remaining marinara sauce.
Cover with foil and bake for 25 minutes, then remove the foil and bake for an additional 15 minutes.
Allow the dish to cool for a few minutes before serving.