In a large pot, over medium-high heat, cook and crumble ground beef until no longer pink. 6-8 minutes; drain. In the same pan, with the ground beef, melt 1 tablespoon of butter over medium heat. Saute onion, carrots, celery, basil, parsley, and Blackstone seasoning(optional) until vegetables are tender, about 10 minutes. Add chicken broth and potatoes. Bring to a boil. Reduce heat; simmer, covered, until potatoes are tender, 10-12 minutes.
Meanwhile, in a small skillet or sauce pan, melt ¼ cup of butter. Add flour, cook and stir until bubbly, 3-5 minutes. Add to soup; bring to a boil. Cook and stir 2-3 minutes. Reduce heat to low. Stir in milk, heavy cream, salt and pepper. Stir until well combined. Add cheese. Cook until cheese melts. Remove from heat; blend in sour cream. If desired, serve with sliced green onions, additional shredded cheese, bacon, and crispy onion rings.