1. Preheat the oven to 375°F and lightly grease a 9×13-inch baking dish.

2. Bring a large pot of salted water to a boil and cook the jumbo pasta shells until al dente according to the package directions. Drain and let them cool slightly.

3. In a large mixing bowl, combine the shredded chicken, ricotta cheese, 1 cup of the mozzarella cheese, 1/4 cup of the Parmesan cheese, 1/2 cup of Alfredo sauce, minced garlic, Italian seasoning, salt, and black pepper. Mix until the filling is creamy and evenly combined.

4. Spread 1 cup of Alfredo sauce across the bottom of the prepared baking dish.

5. Spoon the chicken Alfredo filling into each cooked shell and arrange the stuffed shells in a single layer in the baking dish.

6. Pour the remaining 1 1/2 cups Alfredo sauce over the stuffed shells.

7. Sprinkle the top with the remaining 1 cup mozzarella cheese and the remaining 1/4 cup Parmesan cheese.

8. Cover the dish loosely with foil and bake for 25 minutes.

9. Remove the foil and bake for 10 more minutes, or until the cheese is melted and the sauce is bubbling.

10. Garnish with chopped parsley, let the shells rest for 5 minutes, and serve warm.