When Mr Derek Lai took over Fatty Weng Restaurant in Smith Street in 2013, he assured his father, Mr Lai Foo Weng, 74, that he would keep half of the Cantonese zi char menu intact.

While signature dishes such as deep-fried soon hock fish and honey pork ribs remain, the younger Mr Lai and his head chef Chan Wah Heng, who has been with the restaurant for more than 20 years, come up with innovative new dishes every six months.

This is how the restaurant has stayed relevant since it started in 1967.

Mr Lai says they want to inject fun and variety into the menu of about 100 dishes and to attract a younger generation of diners.

This year's new offerings are deep-fried beancurd with Nonya sauce made with chilli and pineapple and deep-fried wasabi prawns.

Mr Lai, 35, says: "When most young adults dine out, Japanese, Korean and Western cuisines come to mind first. It is only when they are with their parents or older relatives that they choose to dine in Chinese restaurants."

This spirit of innovation is captured in its dish for Singapore Restaurant Month.

The chef rolls up barramundi fillet with mashed potato, seaweed and asparagus, sushi style, and then deep fries it. This dish will be available in the restaurant from July 17 to Aug 2 for $16.80.

It is supposed to pay homage to a classic Cantonese dish of fried garoupa stuffed with duck liver, which is no longer on the menu.

Mr Lai says: "Young people find it difficult to accept the taste of ingredients such as duck liver, so we have replaced it with mashed potato, which has the same velvety texture, and it is also much healthier."

Fatty Weng Restaurant started out as a street-side stall in Albert Street, which sold zi char dishes cooked by the older Mr Lai, whose nickname was Fatty. Business was so good that he upgraded to a 100-seat coffeeshop in Guillemard Road in the 1970s.

At the time, deep-fried soon hock was $8 for 500g and the honey pork ribs were sold at $3 a plate. It is now $35 for 500g and $16.80 respectively.

In its heyday, Fatty Weng also had an 800-seat restaurant in Singapore Badminton Hall in Geylang Lorong 23. It opened in 1986 and hosted many wedding dinners, attended by hundreds of people, and at Chinese New Year, about 1,500 diners would throng the restaurant at dinner time. The restaurant closed in 2007 after the building was accquired by the Government for redevelopment.

The coffee shop outlet was run by Mr Lai's eldest brother, Kelvin, 44, who changed its name to Fatty Lai Restaurant to reflect the family surname. It closed in 2013, after the landlord wanted the space back.

In 2007, the Lais bought over Cantonese restaurant Da Dong in Smith Street, and the restaurant was renamed Da Dong by Fatty Weng.

In 2013, the younger Mr Lai took over the running of the restaurant after Da Dong's founder stepped down, and renamed it Fatty Weng Restaurant. The restaurant is not related to Wing Seong Fatty's Restaurant in Bencoolen Street or other restaurants which have the word "Fatty" in their names.

The younger Mr Lai started out as a kitchen assistant when he was 14, slicing vegetables and fish on weekends and during the school holidays. He went on to cook dishes such as fried rice and stir-fried vegetables.

"Initially, I was not interested in helping out, as my free time was burned, and the older chefs would scold me if things were not done well," he recalls. "But it was good hands-on training that prepared me for my current role."

On preserving the taste of classic dishes, he says that the restaurant has been using the same oyster sauce and a "special sauce for its honey pork ribs" from a supplier for four decades.

He also tweaks his father's hand-written recipes in order to retain the taste of its dishes, despite the fact that the taste of condiments would have changed over the years. The restaurant also offers rarely seen Cantonese dishes, such as braised pig's trotters with black moss and braised duck with lotus seed, which needs to be pre-ordered.

Besides the food, he believes that the restaurant's ambience and service are equally important. During his father's time, "if customers wanted to eat, they jolly well wait". Besides making dishes with less salt upon customers' feedback, his team is refining its plating skills to make dishes more visually appealing or "Instagram ready".

He says: "While it is important to retain the traditional flavours of our food, we have to adapt to modern lifestyles in order to move with the times and attract more customers in this competitive dining scene."