Cheeseburger Soup

1/2 pound 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 flakes
4 T. butter, divided
3 cups chicken broth
4 cups diced peeled potatoes
1/4 cup flour
8 ounces process American cheese, cubed
1 1/2 cups milk
3/4 tsp salt
1/2 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 T. butter until vegetables are tender , about 10 minutes. Add broth, potatoes and beef; bring to a boil. Reduce heat; cover and simmer for 1-2 minutes or until potatoes are tender. Meanwhile, in a small skillet, melt remaining butter. Add flour; cook and stir for 3-5 minutes or until bubbly. Add to soup; bring to a boil. Cook and stir for 2 minutes. Reduce heat heat to low. Add cheese, milk, salt and pepper; cook and stir until cheese melts. Remove from the heat; blend in sour cream.