In a 3 litre saucepan, brown beef; drain and set aside. In the same saucepan, saute onion, 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 for 10-12 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 to low. Add cheese, milk, salt and pepper; cook and stir until cheese melts. Remove from the heat; blend in sour cream.