Heat a large rimmed skillet over medium heat. Add the beef and cook until no longer pink, mincing it with a wooden spoon. Stir in the onion, garlic, and Worcestershire sauce. Cook for 6-8 minutes more, stirring occasionally.

Add the ketchup, mayonnaise, mustard and 4 cups of broth, stir well and bring to a boil. Once the sauce is bubbling, add the macaroni and reduce the heat to a simmer. Cook the macaroni into the sauce, stirring frequently through the bottom of the pan to avoid it from burning. The pasta can easily catch the bottom of the pan if left unsupervised.

Simmer the pasta for about 12-14 minutes, adding the remaining cup of broth when the liquid is mostly absorbed by the pasta. Once the pasta is cooked to al-dente, taste and season with salt and pepper, if needed.

Sprinkle the cheese and cover the pot. Continue to cook over low heat for a couple of minutes more, just until the cheese is melted and bubbly. Garnish with chopped parsley, if desired, and serve immediately while hot.