Ramen shops traditionally let their workers eat noodles in a soup made of the day's leftovers.
Normally the noodles are boiled and put in the soup.
Yet staff didn't have time to wait for the dish to cool, so they came up with the idea of dipping cold noodles in the hot soup and eating them.
This means the ramen picks up the flavours and are still cool enough to eat.
Diners in Japan noted this and asked to try the dish. They gave it the thumbs up. Now this novel idea has come to Hong Kong.
Angela Leung Wai-kwan, who runs the Shugetsu franchise in Hong Kong, says she imported the idea from Ehime, Japan.
"I was wandering the streets of Osaka and walked into Shugetsu," Leung recalls. "I was never a big ramen fan, but I was really impressed by the flavours. I immediately contacted the owner of the company and we agreed to bring the idea to Hong Kong and China."
She says the Japanese owner was keen to promote Japanese culture in other countries. It seemed like a match made in heaven.
Tsukemen involves simply grabbing a small pile of noodles with chopsticks and dipping them into a thick, chicken-based soup.
The soup, a tasty mix of white vinegar, soy sauce and bonito fish essence, is heavily seasoned so that the flavour clings to the noodles. Of course, other "leftovers" are added, usually pork and a smoked egg.
The texture of the ramen is firmer than usual, as it does not continue to cook in the bowl.
Another special feature of eating Tsukemen is that customers pay a flat rate, no matter the size of the portion.
The Hong Kong branch in Gough Street, Central, offers three sizes - 100, 200 and 300 grams. Shops in Japan offer portions of up to 500grams. Hongkongers, with smaller appetites, usually go for 200.
Leung, a former investment banker, says working with a Japanese partner has taught her the value of discipline and perspiration. "Japanese are very disciplined and stick to their principles," she says. "Every bowl of noodles is impeccable, as they pay attention to detail and quality."
Restaurant manager Yoshihiro Takashima appreciates the chance to work outside Japan.
He graduated with a business degree from Drexel University in the US and then decided to be an apprentice at a Shugetsu outlet in Ehime before coming to Hong Kong.
It took him six years to master the skills of making ramen.
"I joined Shugetsu because I wanted to bring traditional Japanese culture to the world," Takashima says. "I am driven to bring Japanese food to the world and coming to Hong Kong has been a dream come true for me."
Leung says locals could learn from Takashima's attitude.
"In Hong Kong, kids are very qualified in their own fields," she says. "That sometimes becomes a weakness. They will not scale down their expectations and embrace what they perceive as inferior jobs, like the catering industry.
"In Japan, people do not think of catering as inferior. They are willing and eager to promote their traditional culture."