Cheeseburger Soup

Melt 1 tablespoon butter in a large pot over medium heat; add ground beef, onion, carrots, and celery. Cook and stir until beef is brown and crumbly, 5 to 7 minutes.

Stir in potatoes, broth, basil, and parsley; bring soup to a boil. Reduce heat to low and simmer until potatoes are tender, 10 to 12 minutes.

Melt remaining 3 tablespoons butter in a small saucepan over medium heat. Add flour; whisk until smooth, about 1 minute. Gradually whisk in milk. Simmer, whisking continuously, until sauce is thick and smooth.

Pour sauce into soup mixture, stirring constantly. Bring to a boil over high heat; reduce heat to low. Add cheese and stir until melted. Add sour cream; stir until just heated through.

Serve garnished with green onions.