Step 1: Preheat your oven to 350°F (175°C).
Step 2: Bring a pot of salted water to a boil. Add the egg noodles and cook according to package directions until al dente. Drain thoroughly and set aside.
Step 3: In a large mixing bowl, combine the cooked chicken, drained egg noodles, cream of chicken soup, sour cream, half of the shredded cheddar cheese, garlic powder, onion powder, and the frozen peas and carrots (if using). Stir gently until evenly combined.
Step 4: Taste the mixture and adjust seasoning with salt and freshly ground black pepper to your liking.
Step 5: Transfer the mixture into a greased 9x13-inch baking dish, spreading evenly.
Step 6: Sprinkle the remaining cheddar cheese generously over the top. If desired, scatter breadcrumbs evenly over the cheese for an extra crispy topping.
Step 7: Bake in the preheated oven for 25-30 minutes, or until the edges are bubbly and the cheese topping is melted and golden brown.
Step 8: Carefully remove from the oven. For a fresh touch, sprinkle with fresh chopped parsley if you like. Allow to cool for a few minutes before serving to let the flavors meld and the casserole set. Enjoy!