Cheeseburger Soup - from Joan

1/2 lb. ground beef
1/2 cup chopped onion
3/4 cup shredded carrots
3/4 cup diced celery
1 tsp. dried basil
1 tsp. dried parsley flakes
4 tbsp. butter or margarine, divided
3 cups chicken broth
4 cups diced, peeled potatoes
1/4 cup all purpose flour
8 oz. processed American Cheese, cubed (I substituted 2% shredded mild cheddar)
1 1/2 cups milk
3/4 tsp. salt
1/4 tsp. pepper
1/4 cup sour cream

In a 3-quart saucepan, brown beef; drain and set aside. In same saucepan, saute onions, carrots, celery, basil and parsley in 1 tablespoon butter until vegetables are tender, about 10 minutes. Add broth, potatoes and beef; bring to a boil. Reduce heat, cover and simmer 10 to 12 minutes or until potatoes are tender.
Meanwhile, in a small skillet, melt remaining butter. Add flour, cook and stir 3 to 5 minutes or until bubbly. Add to soup; bring to a boil. Cook and stir 2 minutes. Reduce heat to low. Add cheese, milk, salt & pepper. Cook and stir until cheese melts. Remove from the heat; blend in sour cream.