Now that Hong Kong is open to the world again, Here's an entry-level list of updated food recs off the top of my head. I've put the focus on HK Island (Central to Wanchai), and Tsim Sha Tsui as that's where most visitors frequent, but if you have specific questions (eg. area-specific, a particular dish or cuisine), I'm happy to answer them!
Cha Chaan Teng (Hong Kong-style cafes, for HK milk tea, baked goods etc.)
Cheung Hing, Happy Valley
Australia Dairy Company, Jordan
Swiss Cafe, Central (not particularly amazing but there aren't that many CCT in Central)
Lan Fong Yuen, Central (see Central comment above)
High-end Cantonese (* indicates dim sum is good too):
The Chairman, Central
Lai Ching Heen*, Regent, Tsim Sha Tsui
Lung King Heen, Four Seasons, Central
Wing, Central
Legacy House, Rosewood, TST
Mid-range Cantonese:
Hong Kong Restaurant 1983*, Happy Valley
Moon Bay*, Wanchai
Low-end dim sum:
Lin Heung Kui*, Sheung Wan
Sun Hong*, Kennedy Town (3am-4pm)
Saam Hui Yat*, Sai Ying Pun (5am-2pm)
Wonton noodles:
Mak's, Central
Mak An Kee Chung Kee, Wing Kut St, Central/Sheung Wan
High-end non-Cantonese Chinese:
Yong Fu, Wanchai
Xin Rong Ji (preorder the Peking duck), Wanchai
Fancy bars:
Darkside, Rosewood, TST
Aubrey, Mandarin Oriental, Central (if you're sugar averse tell them to hold the sugar tho)
The Chinnery, Mandarin Oriental, Central (old school)
Bar Buonasera, TST (Japanese style)
Mizunara, Wan Chai (Japanese style)
Penicillin, Central
The Diplomat, Central (get the burger too)
Happy to answer any specific questions/requests too!