Place beans and 6 garlic cloves in a steamer basket. Place in a large saucepan over 1 in. of water; bring to a boil. Cover and steam for 8-10 minutes or until beans are crisp-tender. Transfer to a large bowl; set aside.
In a small bowl, combine the sour cream, milk and vinegar; let stand for 1 minute. Whisk in the oil, salt, pepper and remaining garlic. Pour over beans and toss. Cover and refrigerate for at least 2 hours. Just before serving, sprinkle with cheese and parsley.