Cook Pasta:
Preheat oven to 375°F (190°C). Cook jumbo pasta shells according to package instructions until al dente. Drain and set aside.

Prepare Filling:
In a bowl, mix ricotta cheese, mozzarella, Parmesan, egg, garlic, Italian seasoning, salt, and pepper until well combined.

Stuff Shells:
Spread a thin layer of marinara sauce on the bottom of a baking dish. Stuff each pasta shell with the cheese mixture and place them in the dish.

Add Sauce:
Pour remaining marinara sauce evenly over the stuffed shells.

Bake:
Cover with foil and bake for 25 minutes. Remove foil and bake an additional 10 minutes until bubbly and cheese is golden.

Serve:
Garnish with fresh basil or parsley before serving.