Har cheong gai is Singapore's take on fried chicken. It's not just crisp outside and juicy inside. It also has a fragrance and umami taste not found in other types of fried chicken. That comes from a marinade made with fermented prawn paste.
There're only 4 ingredients in har cheong marinade:
prawns fermented to a grey goo, aka har cheongoysters fermented to a brown goo, aka oyster saucesugar