I don't think there is the best place, because every mutton restaurant has its own unique flavor and characteristics. Splendid Hotel, Dongjiang Mutton Restaurant, Yiqinyuan Resort and Xinhonglou Restaurant in Chongming District and Zhuanghang Mutton Restaurant in Fengxian District, including Zhuanghang Zhengxing Mutton Restaurant, Li Ji Mutton Restaurant, Jia Zhu Mutton Restaurant, Huajuxuan Mutton Restaurant and Maohuifu Mutton Restaurant, received rave reviews. Zhenru Mutton Restaurant in Putuo District, Xiandian Mutton in Songjiang District and Zhang Ze Mutton Farm are also worth a try.