A spoonful of this tomatoey cheeseburger soup delivers the experience of a perfect burger bite–savory beef and onions, sweet and tangy condiments, and, of course, Cheddar and American cheese! This kid-friendly and easy soup is sure to appeal to everyone in your household.
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. 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.
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.
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/or pickles, if desired.