In a Dutch oven, bring the first 9 ingredients to a boil. Reduce heat; cover and simmer for 10-15 minutes or until potatoes are tender. , Meanwhile, in a large skillet, cook beef and mushrooms in butter over medium heat until meat is no longer pink; drain. Add to soup. Stir in 4 cups milk; heat through. , In a small bowl, combine flour and remaining milk until smooth; gradually stir into soup. Bring to a boil; cook and stir for 2 minutes or until thickened. Reduce heat; stir in cheese until melted. Garnish with bacon.