01 - Preheat oven to 375°F. Grease a 9x13-inch baking dish with cooking spray or butter.
02 - Prepare egg noodles according to package directions until al dente. Drain thoroughly and set aside.
03 - Heat a splash of oil in a large skillet over medium heat. Add onion, carrots, celery, and garlic. Sauté for 4–5 minutes until vegetables are softened and fragrant.
04 - In a large mixing bowl, combine sautéed vegetables, cooked chicken, frozen peas, cream of chicken soup, sour cream, milk, cheddar cheese, thyme, salt, and pepper. Add cooked noodles and fold gently until evenly distributed.
05 - Transfer the mixture to the prepared baking dish, spreading it into an even layer.
06 - Combine panko breadcrumbs, Parmesan cheese, melted butter, and parsley in a separate bowl. Mix until the butter evenly coats the breadcrumbs.
07 - Sprinkle the crumble mixture evenly over the casserole. Bake uncovered for 30–35 minutes until the topping is golden brown and the filling is bubbling around the edges.
08 - Remove from oven and let the casserole rest for 5–10 minutes before serving to allow the filling to set.