Preheat your oven to 375°F (190°C). This will ensure that your Skinny Chicken Parmesan Casserole bakes evenly.
In a large pot, bring salted water to a boil. Add the whole grain penne pasta and cook according to package instructions until al dente. Drain and set aside.
In a skillet over medium heat, add a splash of oil and sauté the bite-sized chicken pieces until they are golden brown and fully cooked, about 5-7 minutes. Season with Italian seasoning if desired.
In a large mixing bowl, combine the cooked pasta, sautéed chicken, marinara sauce, and diced tomatoes (if using). Stir until everything is well coated.
Transfer the pasta mixture to a 9x13-inch casserole dish. Top with the shredded skim mozzarella cheese, followed by the Panko bread crumbs, and finally, sprinkle the grated Parmesan cheese on top.
Place the casserole in the preheated oven and bake for 25-30 minutes, or until the cheese is bubbly and the bread crumbs are golden brown.
Remove the casserole from the oven and let it cool for a few minutes before serving. Enjoy your Skinny Chicken Parmesan Casserole with a fresh salad or your favorite steamed vegetables!
