Cook the jumbo pasta shells according to package instructions until al dente. Drain and set aside to cool slightly.
In a large mixing bowl, combine the cooked chicken, ricotta cheese, half of the mozzarella cheese, Parmesan cheese, minced garlic, Italian seasoning, salt, and pepper. Mix until well combined.
Lightly grease a baking dish with non-stick spray. Spread a layer of Alfredo sauce (about 1 cup) on the bottom of the dish.
Stuff each cooked pasta shell generously with the chicken and cheese mixture, and then place them opening side up in the baking dish.
Once all the shells are stuffed, pour the remaining Alfredo sauce over the top of the shells. Sprinkle the remaining mozzarella cheese on top.
Cover the baking dish with aluminum foil and bake for 25 minutes.
Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and slightly golden.
Remove from the oven and let it sit for a few minutes before serving. Garnish with fresh parsley.
Notes
Let the dish sit for a few minutes before serving for better slicing.