In Sheung Wan, try ABC Kitchen. It's in the Queen Street Cooked Food Market and is essentially the two chefs from a high-end restaurant M at The Fringe which sadly closed some years ago. Good robust European-style dishes. You'll be surprised this kind of place exists in a market.
Try ChomChom in LKF (opposite California Fitness). Good Vietnamese food handmade with care, and sooo cheap for the set lunch.
You sit at the bench and chat to the chef, Peter. Ask him how he makes his broth.
Only $100 (inc service change) for two courses and freshly made Vietnamese drink.