In a large skillet, brown the ground beef over medium-high heat until no longer pink. Drain any excess fat and transfer the beef to a 6-quart slow cooker.
In the same skillet, cook the bacon over medium heat until crisp. Remove with a slotted spoon and transfer to a paper towel-lined plate to drain.
Add the diced onion and garlic to the bacon fat in the skillet and cook until tender, about 5 minutes. Add the onion mixture to the slow cooker.
Add the chicken broth, diced tomatoes, tomato soup, Worcestershire sauce, basil, thyme, salt, and pepper to the slow cooker. Stir to combine.
Cover and cook on low for 6-8 hours or on high for 3-4 hours.
In a separate bowl, whisk together the milk, shredded cheddar cheese, and flour until smooth. Stir the cheese mixture into the soup until well combined.
Cook on high for an additional 15-30 minutes, or until the soup is thick and creamy.
Serve hot, garnished with chopped bacon, shredded cheddar cheese, and green onions, if desired.
