Instructions

1. Cook beef in a large pot over medium-high heat, crumbling with a wooden spoon, until no longer pink, about 5 minutes. Add celery and onion; cook, stirring, until the vegetables are softened, about 3 minutes.
2. Add broth, water and potatoes. Bring to a boil. Reduce heat to a simmer, partially cover and cook, stirring occasionally, until the potatoes are tender, about 15 minutes.
3. Meanwhile, melt butter in a medium saucepan over medium heat. Whisk in flour. Slowly add milk, stirring constantly, and cook until thickened, about 2 minutes. Whisk in tomato paste, ketchup and mustard.
4. Slowly whisk the milk mixture into the soup and bring to a boil. Reduce heat to a simmer and stir in cheese, a handful at a time. Cook just until the cheese is melted. Remove from heat and stir in parsley. Serve topped with tomatoes, onion and relish, if desired.