Butter chicken - one of India's best-known dishes globally - is delicious and apparently also contentious, with two Indian restaurant chains doing battle in court over claims to its origins.

The lawsuit - which has become a hot topic in India - was brought by the family behind Moti Mahal, a famed Delhi restaurant brand that has counted late U.S. President Richard Nixon and India's first Prime Minister Jawaharlal Nehru among its guests.

It claims restaurant founder, Kundan Lal Gujral, created the curry in the 1930s when the restaurant first opened in Peshawar before it moved to Delhi. In a 2,752-page court filing it has sued rival chain Daryaganj, accusing it of falsely claiming to have invented the dish as well as dal makhani, a popular lentil dish that is also laden with butter and cream.

The Gujral family is seeking $240,000 in damages, also alleging that Daryaganj has copied the layout of Moti Mahal's website and "the look and feel" of its restaurants.

"You cannot take away somebody's legacy ... The dish was invented when our grandfather was in Pakistan," said Monish Gujral, managing director at Moti Mahal.

Daryaganj - which was established relatively recently in 2019 - counters that its late family member, Kundan Lal Jaggi, had partnered with Gujral to open the Delhi restaurant in 1947, and the dish was invented there. That gives it the right to also lay claim to the creation of the dish, it argues.

Daryaganj shared with Reuters a faded, hand-written partnership document registered in 1949 to back its argument.

The dispute has captured the nation's attention with Indian TV broadcasters running segments on the history of the dish and debate raging on social media.

"It's an offbeat, unique case. You really don't know who created the first dish of butter chicken. The court will be hard pressed and will need to rely on circumstantial evidence," said Ameet Datta, an intellectual property lawyer at India's Saikrishna & Associates.

Testimonies of people who can link the brand to the dish they consumed decades ago could be critical proof, Datta added.

Made with tandoor-cooked chicken pieces mixed in a tomato gravy with dollops of cream and butter, the dish was ranked 43rd in a list of world's "best dishes" by TasteAtlas as rated by nearly 400,000 users. It was the second-ranked Indian food after butter garlic naan bread. The two are often paired together.

The case was first heard by the Delhi High Court last week and the next hearing is scheduled for May.