Trunk Road is an Indian street-food restaurant based out of an old Darlinghurst terrace house. Run by the team behind Bang, in Surry Hills, Trunk Road only has four menu items and six sides. Actually, that’s not strictly true – it does make a special dish it only offers to cab drivers. But the team won’t tell us what it is.

What we do know is Trunk Road is famous for its Bangladeshi “roadie”. That’s a takeaway roti – chicken, steak, lamb or vegetables, surrounded by salad and wrapped in paratha (northern-Indian flatbread). But users of Deliveroo can try a secret new addition to Trunk Road’s menu, something Trunk Road has never offered before. It’s a curry rooted in family tradition.

“Our offering at Trunk Road focuses on this one particular thing that we’re really good at,” says co-owner Nicholas Gurney, of its well-known roadie. “We thought we’d throw a curry in there for something a little bit different.”

The curry is called From Sylhet with Love. It’s made with chicken, potato, coriander, satkora and pulau rice. The satkora is the key ingredient. It’s a green, knobbly fruit native to head chef Tapos Singha’s home, Bangladesh. (Sylhet is a north-eastern city in Bangladesh). According to Gurney, the fruit is the secret ingredient – it gives the curry its distinctive sour, bitter flavour.

“It’s a family recipe passed down to Tapos from his father,” says Gurney. “This is our opportunity to pass it on to Sydneysiders. It’s not something we would usually do.”

Gurney says the dish is not without controversy. The From Sylhet With Love includes an ingredient Bang and Trunk Road often shy away from: chicken.

“Chicken is kind of a dirty word at Bang,” says Gurney. “People quite often cook chicken at home. We want to cook things for people that they won’t cook themselves.”

Gurney says a curry is the perfect dish for a secret menu item. Everyone knows what it is, but few know precisely what’s in it or exactly how it’s made.

“We want people to understand the effort behind the curry,” says Gurney. “People think a curry is just a jar you buy and that it’s not much work. But a good, traditional curry is actually hours and hours of work.”

The From Sylhet with Love is available until Wednesday July 27, only via Deliveroo.

This article is presented in partnership with Deliveroo.