Preheat oven to 375 degrees F. Spray a 9x13- inch baking dish with nonstick cooking spray; set aside.

Cook pasta shells according to package directions. Rinse with cold water, drain and set aside.

In a large mixing bowl, combine ricotta, 1 cup mozzarella cheese, parmesan cheese, egg, Italian seasoning, salt, pepper and diced chicken.

Spread half the pasta sauce in prepared baking dish. Fill shells with chicken mixture (about 1 heaping Tablespoon of mixture per shell) and place in baking dish.

Once all shells are filled, pour remaining sauce on top of the shells. Top with remaining cup of mozzarella cheese and cover pan with foil.

Bake for 20 minutes then remove foil and bake for an additional 10 minutes or until cheese is melted.