Parts of the movie, produced by Shree Ashtavinayak Cine Vision, have been shot in Kashmir, and so the duo visited the Valley for some special sound work.
One of the line producers from Kashmir is a distant relative of Imtiaz and he invited the director, along with Rahman, to his place for a treat, says a source from the unit of the film.
There they were treated to authentic Kashmiri delicacies like Vaazwan, cooked by the lady of the house.
What followed was a routine where almost every day, Vaazwan was brought to the sets for the unit to relish.
On the last day of their schedule, the team called for a huge feast with a variety of Kashmiri delicacies and everyone present on the sets including actors Ranbir Kapoor and Nargis Fakhri enjoyed it.
"Rockstar" is set to release Nov 11. The film is about a young super-successful musician who doesn't believe in love, but deliberately falls in love on the advice of a musician to enrich his musical sense and become emotionally richer.