Preheat the oven to 375°F (190°C).

Cook the jumbo pasta shells according to the package instructions until al dente, usually around 9-11 minutes.

In a mixing bowl, combine ricotta, mozzarella, Parmesan, egg, parsley, garlic powder, Italian seasoning, salt, and pepper.

Drain the pasta shells and let them cool slightly before stuffing.

Spoon the cheese filling into each shell, about 2 tablespoons per shell.

Spread a layer of marinara sauce on the bottom of a baking dish.

Place the stuffed shells seam-side up in the baking dish and top with remaining marinara sauce and a sprinkle of mozzarella.

Cover the baking dish with aluminum foil and bake for 25 minutes.

Remove the foil and bake for an additional 10-15 minutes until the cheese is bubbly and golden.

Let the stuffed shells cool slightly before serving.