Cook the noodles: Bring a large pot of salted water to a boil. Cook egg noodles according to package instructions until just al dente. Drain, return to pot, and toss with butter. Set aside.
Mix the sauce: In a large bowl, whisk together cream of mushroom soup, sour cream, beef broth, Worcestershire sauce, garlic powder, onion powder, black pepper, and nutmeg if using.
Assemble the casserole: Preheat oven to 350°F (175°C). In a greased 9×13-inch baking dish, mix the cooked noodles with the sauce until evenly coated. Gently fold in the frozen meatballs.
Top with cheese: Sprinkle shredded cheese evenly over the top.
Bake: Cover loosely with foil and bake for 25 minutes. Remove foil and bake for another 10 minutes, or until the cheese is melted and bubbling.
Serve: Garnish with fresh parsley if desired. Serve hot and enjoy!
