1. In a large skillet, cook the ground beef over medium heat until no longer pink. Drain any excess fat.
2. Add the chopped onions and minced garlic to the skillet with the browned beef and cook for another 3-4 minutes, until the onions are translucent.
3. Transfer the beef mixture to your slow cooker. Add the chicken broth, diced potatoes, carrots, celery, dried basil, and dried parsley flakes.
4. Cover and cook on low heat for 6-8 hours, or until the vegetables are tender.
5. Thirty minutes before serving, mix the milk and flour in a small bowl until smooth. Stir this mixture into the slow cooker along with the shredded cheddar cheese.
6. Continue to cook for another 30 minutes, stirring occasionally, until the cheese is melted and the soup is thickened and creamy.
7. Just before serving, stir in the sour cream. Add salt and pepper to taste.
