Bring a large pot of salted water to a rolling boil. Add egg noodles and cook according to the timing on the package until they reach an al dente texture. Drain well, return the noodles to the pot, and stir in the butter to coat. Set aside.
In a large mixing bowl, combine the cream of mushroom soup, sour cream, beef broth, Worcestershire sauce, garlic powder, onion powder, black pepper, and nutmeg (if using). Whisk thoroughly until smooth and fully incorporated.
Preheat your oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish. Transfer the buttered noodles to the dish and pour the prepared sauce over them. Toss gently to ensure the noodles are thoroughly coated. Carefully fold in the frozen meatballs.
Evenly distribute the shredded cheese over the top of the casserole.
Cover the dish loosely with foil and place it in the oven. Bake for 25 minutes. Remove the foil and continue baking for an additional 10 minutes, or until the cheese is melted and the edges are bubbling.
If desired, sprinkle with chopped fresh parsley just before serving. Present hot from the oven.