Classic Cheeseburger Soup



1 teaspoon light oil
1 small onion, chopped
½ cup celery, chopped
2 cloves garlic, minced
1 pound ground beef
1 teaspoon dried basil
2 tablespoons all-purpose flour (may substitute corn starch for gluten-free option)
5 cups reduced-sodium beef broth
2 medium potatoes, chopped into bite-sized pieces
1 14.5-oz. can diced tomatoes, do not drain
Cheese - select one of these 3 options: 10 ounces Velveeta, cut into 6 pieces, or 14 slices American cheese slices, or 10 ounces medium cheddar cheese, shredded
1 6-oz. can tomato paste
⅓ cup ketchup
3 tablespoons Dijon-style mustard (may substitute for regular mustard)
1½ cups whole milk
Assorted condiments: Pickles, diced fresh onions or scallions, black or green olives, crispy-cooked bacon crumbles, more shredded cheese (try bleu cheese), fresh tomatoes
Croutons or homemade crostinis, to simulate a classic bun