Preheat the oven to 375 degrees. Prepare two 9x13 casserole dishes with nonstick cooking spray.
In a large skillet over medium high heat, melt the butter. Add the onions and cook until the onions are softened, about 3 to 5 minutes.
Sprinkle the flour over the onions, stirring well. Gradually stir in the beef broth, Worcestershire sauce, salt and black pepper.
Reduce the heat to medium and continue to cook for 3 to 5 minutes, stirring occasionally, until the mixture has thickened. Add the cream cheese and stir until melted. Remove the mixture from the heat and stir in the heavy whipping cream.
In a very large bowl, combine the noodles, meatballs, and sauce.
Divide the noodle mixture between the casserole dishes. Cover the casserole dishes with aluminum foil and bake for 30 to 35 minutes.