1. Cook the jumbo pasta shells in a large pot of salted boiling water until just al dente according to package directions. Drain, then spread the shells in a single layer on a lightly oiled baking sheet to cool.

2. Preheat the oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish.

3. In a large mixing bowl, combine the ricotta, 1 1/2 cups of the shredded mozzarella, 1/2 cup grated Parmesan, egg, minced garlic, Italian seasoning, salt, and black pepper. Stir until smooth and well blended.

4. Add the shredded chicken to the cheese mixture and fold gently until the chicken is evenly coated and the filling is thick and scoopable.

5. Spread about 3/4 cup of the Alfredo sauce over the bottom of the prepared baking dish to lightly coat it.

6. Spoon the chicken and cheese filling into each cooled pasta shell, packing it in firmly without overfilling. Arrange the stuffed shells snugly in the baking dish in rows.

7. Pour the remaining Alfredo sauce evenly over the stuffed shells, making sure each shell gets a good drizzle of sauce.

8. Sprinkle the tops of the shells with the remaining 1/2 cup shredded mozzarella and 2 tablespoons grated Parmesan.

9. Cover the baking dish loosely with foil and bake for 20 minutes, until the sauce is bubbling around the edges.

10. Remove the foil and bake for an additional 8–10 minutes, or until the cheese on top is melted and lightly golden.

11. Let the shells rest for 5 minutes, then sprinkle with chopped fresh parsley and serve warm with extra Alfredo from the pan spooned over each portion.