Preheat oven to 350F Have a small casserole dish ready.
Bring a large pot of salted water to a boil. Cook the shells for 10 minutes. Drain and let cool.
In a large bowl, mix together the ricotta, 1 cup mozzarella, parmesan, salt, basil, and the egg.
Spread 1/4 cup sauce on the bottom of the casserole dish. Stuff each shell with a small amount of the ricotta cheese mixture and place closely together in the dish. Top with remaining sauce and mozzarella cheese. Cover with foil and bake for 20 - 25 minutes. Remove the foil and bake for another 5 -10 minutes or until the cheese is melted on top.