Cook the pasta shells: Cook the jumbo pasta shells according to the package instructions. Drain and set aside to cool slightly, so they are easier to handle when filling.

1. Prepare the filling: In a large mixing bowl, combine the shredded chicken, cream cheese, sour cream, taco seasoning, cheddar cheese, and green onions. Stir until the mixture is smooth and well combined.
2. Stuff the shells: Preheat the oven to 375°F (190°C). Stuff each cooked pasta shell with the chicken mixture, pressing gently to ensure they are filled evenly. Place the stuffed shells in a greased 9×13-inch baking dish.
3. Top with sauce: Pour the enchilada sauce evenly over the stuffed shells, ensuring they are all covered. Sprinkle the shredded mozzarella cheese on top (if using).
4. Bake: Cover the baking dish with aluminum foil and bake in the preheated oven for 20-25 minutes, or until the cheese is melted and bubbly. If you want the cheese to be golden brown, remove the foil during the last 5 minutes of baking.
5. Garnish and serve: Once the shells are baked, remove from the oven and let cool for a few minutes. Garnish with fresh cilantro before serving for a burst of color and flavor.