The result is Milktealogy, a series of comic strips that has evolved into a light-hearted, online cultural magazine about everything to do with the archetypal Hong Kong drink and the people who make it.

"After years of drinking milk tea, we realised that, as well as being addictive, it is a local icon. There are a lot of stories behind the drink and most people don't know about them," says Ka-long.

"We are eager to keep this project running because we want to document a history that is often taken for granted and some memories that are fast disappearing."

Launched on Facebook and Instagram last March, Milktealogy includes tastings and interviews with veteran tea makers and owners of local diners, known locally as cha chaan teng. It now has more than 13,000 followers on the social networks.

"Coffee and red wine are often considered high-end drinks and symbols of a quality lifestyle, but we believe milk tea deserves the same respect, if not more," says Ka-hei.

"The origin of the tea leaf, how it is roasted and brewed, is just as significant [in tea-making] as that of coffee beans, or of the terroir and fermentation of grapes in winemaking."

According to these two tea lovers, the tastiest cuppas usually comprise a blend of 70 per cent brewed tea, 20 per cent evaporated milk and 10 per cent sugar.

The blend of tea leaves, the water temperature, the ratio of evaporated milk to the tea and the way it is poured are all important in making the perfect Hong Kong cuppa. And the brothers reckon an old-style ceramic cup is best for serving tea because it has the best insulation, and the thick, rounded rim gives a greater area of contact for savouring a smooth brew.

They also believe the customs and anecdotes surrounding the drink are just as precious.

"We use milk tea as a starting point to conduct an exploration of cha chaan teng culture and, by extension, the Hong Kong way of life," says Ka-hei. "We're not making a food programme where we analyse the taste of each cup of milk tea. The people, and the story behind each place we visit are equally important."

With this in mind, their reviews of tea houses rate the ambience, as well as the smoothness and fragrance of the tea.

The twins also create humorous comic strips about local food culture as seen through the eyes of two fictional characters, Benny and Miss M. These have struck a chord with both locals and tourists.

Detailed illustrations encapsulate their research into the use of tea leaves, drinks containers and food pairing options such as French toast and egg tarts.

The pictures also reflect their observations of the waiters' witty shorthand notes, as well as their efficiency.

Their first illustration featured Tak Yu, a family-run cha chaan teng tucked away in a corner of gentrifying Star Street in Wan Chai. They have documented about 30 places so far, excluding those that weren't good enough to deserve a write-up.

Followers of the series may have noticed some teasers that hint at interviews with cafe owners and that have yet to be made public.

These write-ups, they reveal, will only be found in a book that they hope to publish this year. "The tech-savvy younger generation wants instant gratification, so we don't want to waste the full interviews by putting them online," says Ka-hei. "Anyone intrigued by our Facebook page will be able to find out more from our book."

In their quest to document idiosyncratic and unusual tea places, the brothers have highlighted places such as Cheng Kee Store in Sham Tseng. This uses wok-fried tieguanyin, instead of the usual red tea, for an award-winning milk tea.

But they also found that many distinctive shops have been forced to close because of astronomical rents, including Wing Fat Restaurant and Bakery, in Sham Shui Po.

Milktealogy touches on subjects including the small businesses having to close due to high rents, and the umbrella movement.

When the sit-in began, the twins halted the Milktealogy postings, feeling that the material was inappropriate for a time of such upheaval. But they soon resumed publishing - with illustrations inspired by the pro-democracy protests.

"There are many reasons why a shop closes, but ridiculous rents are one of the main causes. Ageing owners have to shut down abruptly before they can find someone to inherit their shop because they can no longer afford the rent. That is such a pity," says Ka-hei.

"We're trying our best to keep this local culture alive. We don't have the experience to start a cha chaan teng or make a cup of milk tea, but we're using what we're good at - art and creation - to play a part in preserving its culture."

The Tsui brothers and their partners at Zcratch, who are all graduates of Polytechnic University or City University, like to draw inspiration from the city where they were born.

Zcratch's first animated work, (2005), was a send-up of the local education system. Featuring Bruce Lee fighting his way into a well-defended Examination Authority headquarters, the clip won a special mention in that year's ifva (film and visual media) awards organised by the Hong Kong Arts Centre.

A 2006 video titled explored the controversy about bringing the Disney theme park to Hong Kong. It has been a tough 10 years for the creative team but they are finally starting to get some attention.

They were hired for the post-production work on two 2014 film projects, the comedy and Jessey Tsang Tsui-shan's documentary . More recently, they produced a television commercial featuring Hong Kong's favourite cartoon pig McDull for the Council on Smoking and Health.

The brothers lament that most of their non-commercial work has only been seen at film festivals, or in competition screenings, and hope the Milktealogy project will reach a wider audience.

Milk tea was deservedly included on Hong Kong's inventory of intangible culture heritage, but the twins think a lot more should be done to preserve the unique drink that was adapted from the afternoon tea tradition of the British colonialists - and quickly.

"The so-called free market is actually not that free at all. It's all under the shadow of corporate monopoly," Ka-long says. "Economic efficiency shouldn't always come first. We don't want to see a day when machine-made milk teas made with the same formula are all that's available.

"Even if they can replicate the taste, they won't be able to retain the culture and flavour," he says.