Bring 4 quarts of water to a boil and cook the pasta according to package directions.

While the pasta is being prepared, brown the ground beef along with the onion, salt, pepper, and garlic.

When the beef is completely cooked do not drain the grease. Stir in the flour to coat the beef. Cook for 2 minutes over medium heat.

Slowly whisk in the milk and bring to a low simmer over medium low heat. Do not boil.

When the milk mixture is beginning to bubble gently, stir in the cheese. Stir until all the cheese is melted. Turn off the heat.

When the pasta is finished cooking, drain and place back into the pot it cooked in.

Stir the cheese sauce into the pasta and serve with mustard and ketchup drizzle and chopped tomatoes.