1. 1. Prepare the Pasta Shells: Bring a large pot of salted water to a boil. Add the jumbo pasta shells and cook according to package directions until al dente. Drain the shells and rinse them with cold water to prevent sticking. Lay them out on a baking sheet or clean surface to cool slightly while you prepare the filling.

2. 2. Preheat Oven and Prepare Baking Dish: While the shells are cooling, preheat your oven to 375 F (190 C). Lightly grease a 9×13-inch baking dish. Pour about half of the jarred Alfredo sauce into the bottom of the prepared baking dish, spreading it evenly.

3. 3. Create the Creamy Filling: In a large mixing bowl, combine the cooked shredded or diced chicken, finely chopped fresh broccoli florets, ricotta cheese, 1/2 cup grated Parmesan cheese, the large egg, garlic powder, and black pepper. Mix everything thoroughly until all ingredients are well combined and the mixture is uniform.

4. 4. Stuff the Pasta Shells: Carefully pick up each cooked pasta shell and gently open it. Using a spoon or a small cookie scoop, fill each shell generously with the chicken and broccoli-ricotta mixture. Don’t overstuff them, but make sure they are nicely filled.

5. 5. Arrange and Sauce the Shells: Arrange the stuffed shells in a single layer in the prepared baking dish over the Alfredo sauce base. Once all shells are placed, pour the remaining Alfredo sauce evenly over the top of the stuffed shells, ensuring they are well coated.

6. 6. Add the Final Layer of Cheese: Sprinkle the 1/2 cup shredded mozzarella cheese over the sauced shells. You can also add a little extra grated Parmesan cheese at this point if desired for an extra cheesy crust.

7. 7. Bake Until Bubbly and Golden: Place the baking dish in the preheated oven and bake for 25-30 minutes, or until the sauce is hot and bubbly, and the mozzarella cheese on top is melted and lightly golden brown. If you like a crispier top, you can briefly broil for 1-2 minutes at the very end, watching carefully to prevent burning.

8. 8. Rest and Serve: Remove the dish from the oven and let it rest for 5-10 minutes before serving. This allows the filling to set slightly and prevents burns from the hot sauce. Serve hot, garnished with fresh parsley if desired.