I didn’t try this one either, but I always saw long lines waiting outside in their Causeway Bay shop (84 Pervival Street), it’s called Chee Kei. It’s comparatively more recent, only since 1994. But has already 4-5 shops everywhere in HK.
(photo from their website)
PS I just saw there’s another link on Hungry Onion talking about the restaurant but not wanton noodle:
