Preheat the oven to 375°F and lightly coat a 9x13-inch baking dish with nonstick spray; set aside.

In a large mixing bowl, combine ground beef, breadcrumbs, beaten egg, grated onion, ground nutmeg, garlic powder, salt, and black pepper. Shape the mixture into 1 1/2-tablespoon-sized balls.

Warm olive oil in a large skillet over medium-high heat. Sear the meatballs until browned on all sides; they do not need to be cooked through. Remove the browned meatballs and set aside.

Bring a large pot of salted water to a boil. Cook the egg noodles for approximately 2 minutes less than the package instructions, then drain.

Using the same skillet where the meatballs were browned, pour in the beef broth, heavy cream, and Worcestershire sauce. Scrape the bottom to incorporate any browned bits. Simmer the sauce for about 10 minutes until it thickens slightly. Season with salt and pepper.

Place the cooked noodles into the prepared baking dish and arrange the meatballs throughout. Evenly pour the cream sauce over the entire dish and sprinkle with grated Swiss cheese.

Bake for 20 minutes or until the cheese is bubbling and fully melted. Let the casserole rest for 5 minutes before garnishing with chopped parsley and serving.