In a large pot of boiling salted water, cook the jumbo shells according to package instructions until al dente. Drain and set aside to cool slightly.
In a mixing bowl, combine the cooked, shredded chicken, ricotta cheese, half of the mozzarella cheese, Parmesan cheese, garlic powder, Italian seasoning, salt, and pepper. Mix until well combined.
Take each cooled pasta shell and spoon in a generous amount of the chicken mixture, ensuring each shell is well-filled.
In a 9x13-inch baking dish, spread 1 cup of the Alfredo sauce evenly on the bottom. Arrange the stuffed shells on top of the sauce, then pour the remaining Alfredo sauce over the shells.
Sprinkle the remaining mozzarella cheese over the top.
Cover the baking dish with aluminum foil and bake in the preheated oven for 25 minutes. Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbling and golden.
Remove from the oven and let it cool for a few minutes. Garnish with chopped fresh parsley before serving.
Notes
Feel free to use homemade Alfredo sauce for a richer flavor.