"Our regular customers are now such aficionados of the dish that they can tell whether a new or more experienced chef cooked the duck, just by looking at how crispy it is," says the 48-year-old.

After it's marinated and steamed, the duck is sliced down the spine and placed back-down on a plate. After it has been fried, the duck is turned over to show its perfectly crispy belly, and served to guests together with sauce, shredded scallions and thin pancake.

Ma says that when he first learned how to make the dish, around 12 different traditional Chinese herbs were used to stuff the duck. The ongoing process of upgrading the flavor now sees around 20 different ingredients being used in the recipe, all supplied by Tongrentang, the country's largest producer of traditional Chinese herbal medicines.