Preheat oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish.
Cook egg noodles in salted boiling water until just al dente. Drain and set aside.
In a large mixing bowl, combine cream of chicken soup, sour cream, melted butter, onion, garlic, salt, and black pepper. Stir until smooth.
Add cooked chicken and noodles to the sauce. Mix gently until everything is evenly coated.
Transfer the mixture to the prepared baking dish. Stir in cheese or vegetables if using.
Cover with foil and bake for 25–30 minutes.
Remove foil and bake uncovered for an additional 10–15 minutes until hot and bubbly.
Let rest for 5 minutes before serving.