Hakka Tea, as it is called, is a dying form of tea in Hong Kong. The tea consists of pounded tea leaves and a variety of other ingredients, such as peanuts, salt, puffed rice and sesame seeds. Other ingredients are also often added to give the tea different nutrients and flavours. By consuming Hakka tea, a person is able to both drink and eat at the same time, making it ideal for snacks.
Despite the tea having been around for centuries, it is currently in a slump. Only some members of the older generation continue to make it, and many of the Hong Kong locals do not know of its existence.
You can read more about Hakka tea here: http://rachanahkbu.wordpress.com/2014/05/18/hakka-tea-in-hong-kong-fades-into-oblivoi/comment-page-1/#comment-7