Begin by cooking the jumbo pasta shells according to the package instructions until al dente. Drain and set aside on a baking sheet to cool slightly.
In a large skillet, heat the olive oil over medium heat. Add the ground chicken (or small pieces of chicken breast) and season with dried Italian seasonings and salt. Cook until the chicken is no longer pink, about 5-7 minutes. Remove from heat and let cool.
In a mixing bowl, combine the ricotta cheese, 1 cup of the shredded mozzarella, grated Parmesan cheese, egg, minced garlic, and 1/2 teaspoon of salt. Mix well until all ingredients are fully incorporated. Fold in the cooked chicken until evenly distributed.
Preheat your oven to 375°F (190°C). In a baking dish, spread a thin layer of marinara sauce on the bottom. Using a spoon, carefully fill each cooked pasta shell with the chicken and cheese mixture. Place the filled shells seam-side up in the baking dish.
Once all the shells are filled and in the baking dish, pour the remaining marinara sauce over the top of the shells. Sprinkle the remaining mozzarella cheese and Panko breadcrumbs evenly over the sauce.
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 bubbly and golden brown.
Once baked, remove the Chicken Parmesan Stuffed Shells from the oven. Allow them to cool for a few minutes before garnishing with chopped parsley, if desired. Serve hot and enjoy!