Bring a large pot of salted water to a boil. Cook jumbo pasta shells until al dente, about 8–10 minutes. Drain and cool slightly.

In a large skillet, heat olive oil. Brown ground beef or sausage for 5–7 minutes. Drain fat and let cool.

In a mixing bowl, combine cooked meat with ricotta, half of mozzarella, Parmesan, egg, and herbs. Season with salt and pepper, stirring until blended.

Preheat oven to 375°F (190°C).

Fill each cooled shell with meat mixture, arranging them in a baking dish.

Pour marinara sauce over the shells, ensuring each shell is covered.

Sprinkle remaining mozzarella over the shells.

Cover dish with foil and bake for 25 minutes. Remove foil and bake for an additional 15 minutes.

Let cool for a few minutes and garnish with parsley before serving.