They are well-known for their fresh hand-made noodles with Shrimp Roe (you can buy the Shrimp Roe by the bottle but I'm not sure how immigration will feel about you exporting some though). Their Crab Congee is popular and excellent. I can close my eyes and taste the inherent sweetness in their Dungeness crab.
Wong Kun Sio Kun is actually a Bib Gourmand pick in the Michelin guide (2015). It is constantly featured in Chinese media so I first heard of it from my sister-in-law. The following review is from my 2 separate visits to the restaurant.
But the food and friendly service totally makes up for the (lack-of) ambiance.
On the first visit, the friendly owner chatted with us for a bit. Since then, business has been so good that he has expanded to two new locations (I think one is near the Ruins of St. Paul), and another at the Galaxy Hotel ( I've only been to the original branch shown here). It is now one of my favorite restaurants in Macau. To make things easier, they now have English Menus (I didn't try speaking English with the staff so I'm not sure if they would be able to converse).
If you can read Chinese, or don't mind using a translator, they do have an official webpage .
With an order of Curry Crab and Crab Congee, it won't be the cheapest meal you will have in Macau, but it's certainly worth every penny (or Patacas). For reference, 3 dishes for two-- 1/2 order Curry Crab (yes you can get half order) + Crab Congee with 1 crab + a plate of Shrimp Roe noodles will run you around $950 MOP | ~ $120 usd. For the full-on order of Curry Crab and enough food to feed a party of 4+, expect a bill around 2k MOP+ ($250 usd+) which is still a pretty good price for an excellent meal. You could opt to order non-seafood items, but that would almost defeat the purpose of going here.