When I need to get my fix for authentic Cantonese food in Tokyo, I found this China House Bekkan in Roppongi to fulfill it. I found that a lot of the Chinese restaurants in Tokyo with the exception of a few, offer a quasi Japanese Chinese variation(chuka ryori) on a certain Chinese cuisine, something similar to passing off chow mein and sweet and sour pork being authentic Chinese food in the US many years ago. Their chef is formally trained in Hong Kong and you can pretty much tell from the various dishes that the wok chi is present.
I usually sit at the counter and usually have their Chinese beef stew (ngow nam fan) served over rice. It's one of the best tasting beef stews I've ever eaten and I've had this dish in Hong Kong, Singapore, and the US in various cities and haven't come across anything tastier. Also their congee and wonton noodles is similar in taste as any you would find in HK. A nice Chinese lady is usually preparing and serving the various short order dishes from behind the counter but speaks only Japanese, Mandarin, or Cantonese.
They have daily specials which I've tried, most notably a drunken chicken dish that was delicious.
A few years back, I went to this fabulous Chinese restaurant in the Fukoku Seimei Building, 28th floor called Heichinrou. One of the best Chinese banquet meals I've ever tasted outside of Hong Kong and Los Angeles. Shark fin soup in a super duper supreme broth (or spiked with tons of ajinomoto), mushroom with abalone, a lobster dish, a few creatively presented and tasty dishes which I have yet to come across anywhere else. I can't even find it in the States. I should've written down the names of the dishes we ate but it seemed impolite at the time. The person who invited us seemed to have ordered a few dishes that weren't on the menu but knew either the maitre 'd or the chef well enough to indulge us with something special. Sometimes I can't tell until after I finish the meal if I suffered an MSG high, I would know how authentic the flavor really was. Since I didn't experience that or had to drink a trough of mizu then I figure it was authentically and richly flavored. It was 4 of us and low six figure yen bill.
China House Bekkan
5-18-2 Roppongi, Minato-ku
Fukoku Seimei Building 28F
2-2-2 Uchisaiwai-cho, Chiyoda-ku