Preheat your oven to 350°F (175°C).

Bring a large pot of salted water to a gentle boil and cook the jumbo shells according to package instructions until al dente, usually about 8-10 minutes.

Carefully drain the shells and lay them out on a clean kitchen towel to cool slightly.

In a sizable bowl, combine the ricotta, half of the mozzarella, grated Parmesan, egg, chopped basil, salt, and pepper. Mix until well incorporated.

Using a spoon, take a generous scoop of the ricotta mixture and stuff each shell, then set aside on a plate.

Pour about a cup of marinara sauce onto the bottom of a 9x13 inch baking dish.

Arrange the stuffed shells on top of the sauce in a single layer, leaving a little space between them.

Drizzle the remaining marinara over the top and sprinkle with the remaining mozzarella cheese.

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

Remove the foil and continue baking for another 10-15 minutes until the cheese is bubbling and slightly golden.