There is a rather smart Chinese restaurant in Shirokane's Platina Dori called Shirokanetei. You'll find it between the new Oslo Cafe and the new The Tender House towards the top of the street. Shirokanetei is not new and has evidently stood the test of time.
I haven't tried the somewhat upmarket dining room on the 2nd floor, but recently tried their all you can eat yum cha on the first floor. It has a slightly oddball feeling to it - like a breakfast bar in a small hotel and, although they're totally competent, the staff like to take things at their own pace. For 2,480 yen you can order all the dim sum you can eat from the menu (about 30 choices) and there is also a small buffet where you can have hot and sour soup, corn soup, fried noodles, mapo tofu and dessert.Tea and other drinks attract an additional charge.
Overall it's great value for money and the food is not bad. The most interesting thing I tried was the foie gras soup dumpling. Surprisingly good.