In a large pot or deep skillet, heat the olive oil or butter over medium heat. Add the chopped onion and cook until softened, about 3-4 minutes.
Add the minced garlic and cook for another 1-2 minutes until fragrant.
Add the ground beef, breaking it up with a spoon as it cooks. Cook until the beef is browned and fully cooked through. Drain any excess fat.
Stir in the ketchup, mustard (if using), broth, milk, and diced tomatoes with their juice. Bring the mixture to a boil.
Once boiling, add the uncooked pasta. Reduce the heat to a simmer and cover the pot. Cook for 10-12 minutes, stirring occasionally, until the pasta is tender and has absorbed most of the liquid.
Once the pasta is cooked, stir in the shredded cheddar and mozzarella cheese until melted and the dish is creamy. Season with salt and pepper to taste.
Serve the cheeseburger pasta warm, topped with your choice of optional toppings like diced pickles, parsley, or extra cheese.