Cheeseburger Soup

½ lb ground beef
3/4 cup chopped onion
3/4 cup shredded carrots
3/4 cup diced celery
1 tsp dried basil
1 tsp dried parsley
4 Tbsp butter or margarine, divided
3 cups chicken broth
4 cups diced peeled potatoes (1-3/4 lb)
1/4 cup all-purpose flour
8 oz american cheese cubed (i.e. Velveeta)
1-1/2 cups milk
1/4 tsp pepper
1/4 cup sour cream

In a 3 qt. saucepan, brown beef; drain and set aside. In the same saucepan, saute onion, carrots, celery, basil and parsley in 1 Tbsp butter until vegetables are tender, about 5 min. Add broth, potatoes and beef; bring to a boil. Reduce heat; cover and simmer for 5 min or until potatoes are tender. Meanwhile, in a small skillet melt remaining butter. Add flour; cook and stir. Add to soup; bring to a boil. Cook and stir reduce to low heat. Add cheese, milk, salt and pepper; stir until melted. Remove from heat and blend in sour cream.