Seaweed Four Treasures is my favourite dish in Hong Kong. The four treasures are mushroom ball, squid ball, fish cake and fish paste (varies in different restaurant but mushroom ball will definitely be included).
I personally like the mushroom ball 香菇贡丸 for its texture and strong fragrant sesame oil from within.
It can be found easily in almost every local coffee shop/restaurant in the city. Served with clear soup or choice of rice noodles, flat rice noodles or noodles.