Heat the oven to 375°F and grease a 9x13-inch baking dish with nonstick spray.

In a large bowl, mix the ground beef, breadcrumbs, egg, onion, nutmeg, garlic powder, 1 teaspoon salt and 1/2 teaspoon pepper. Scoop the mixture out 1 1/2 tablespoons at a time and roll into balls.

Heat the olive oil in a large skillet over medium-high heat. Add half the meatballs and brown them on all sides, then move them to a plate and repeat with the rest. They will not be cooked through yet; they finish in the oven.

While the meatballs brown, bring a large pot of salted water to a boil and cook the egg noodles 2 minutes less than the package says. Drain.

Add the beef broth, heavy cream and Worcestershire sauce to the same skillet, scraping up the browned bits on the bottom. Simmer until slightly thicker, about 10 minutes. Season with salt and pepper and take it off the heat.

Spread the noodles in the baking dish and nestle the meatballs into them. Pour the sauce evenly over the top and sprinkle with the Swiss cheese.

Bake for about 20 minutes, until the cheese is melted and bubbly, the center of a meatball reads 160°F and the center of the casserole reaches 165°F on a food thermometer.

Let the casserole sit for 5 minutes, then sprinkle with chopped parsley and serve.