For Hong Kong, I think sck named a lot of good places. Just a few more:
If you want the quintessential (aka brusque manner) HK style cafe (cha chan tang) style breakfast I’d say check out Australia Dairy Company. They did a fantastic scrambled egg. Other wise, I had a good time at Capital Cafe as well. Though I don’t know if its the HK preference, but I found most places that serve macaroni to be on the very soft side (I prefer al dente).
Won ton soup was mentioned, but I enjoyed Mak’s Noodle on Wellington.
One topic I don’t think anyone ever really talked about are pineapple buns. I really enjoyed the ones at Kam Wah (for an extra punch, get a pineapple bun with a slab of ice cold butter in between).
For other bbq roasties, I liked Joy Hing’s char siu but I agree with Kam and Yat Lok for roast goose.
I don’t know exactly when you’ll be going, but for an interesting experience check out Ser Wong Fun or Se Wong Yee for some snake soup! I had Se Wong Yee’s double boiled soup as well and they did a fantastic job. Usually recommended to eat around winter time, but eh… I don’t mind it at any point, haha.
For clay pot rice I had a pretty tasty meal at Four Season Pot Rice.
Regarding dim sum, I recommend trying one of the top tier dim sum places (Lung King Heen, Tin Lung Heen, etc.). However on the side, I suggest Tim Ho Wan and their famed bbq pork buns; a must get I’d say. The sham shui po one or olympian city location is in theory closer foot wise, but might be easier just to take the MTR to the IFC location and grab a to go order.
Cantonese dinner places… there are tons to choose from but for higher ended versions, I actually quite enjoyed the double boiled soups at Lei Garden (multiple locations) and their dinner. Another suggestion is The Chairman, though some people have felt that it has dipped a little in quality, I’ve enjoyed both meals when I went (April 2015, and Oct 2016). Note, one of their chefs started their own restaurant that sck recommended --Tasting Court. A little bit different in approach, the Chairman is like a Californian (Alice Waters, etc.) take on Cantonese cuisine while Tasting Court is a return to older traditions.
Now, one thing that is more akin to street foods, the old school dai pai dong’s. One really interesting one is Tung Po which was featured on Anthony Bourdain’s No Reservations. Fantastic wok hei. A throw back to a tasty breakfast in central, check out Sing Heung Yuen. A little campy, and to some the food is odd, but for some reason the beef and tomato macaroni in soup just hit the spot for me. Check out their toast as well!
For dessert places, check out Hui Lau Shan for their pomelo, mango, sago dessert (note, I believe Lei Garden was the one that invented the dish but oddly I never actually tried it there; the one at Yan Toh Heen was fantastic as well).