"I wanted to find personal stories from among them. Instead we became friends and they started telling stories about the housewives they would pick up lunchboxes from," Batra said.

"I got more interested in that. So I abandoned the documentary and started writing this," said the director, who has won the Best Debut Director prize at the prestigious 2014 FilmFare Awards for the film.

That was the genesis of the film set to release in New York and Los Angeles on Friday after a stellar run at the world's top film festivals including Cannes, Toronto, and Sundance where it met with rave reviews.

It then opens March 7 in San Francisco, Washington DC, Chicago and other major US cities.

Batra never anticipated the way the film seems to have taken both India and the West by storm.

"You are just trying to be honest to every moment of the film," he said. "It's hard enough to make a film. To anticipate what it's going to do later is just impossible."

The story revolves around Ila, a young middle class Mumbai housewife, trying to win back her husband's affections through his stomach and how a rare mistaken delivery in Mumbai's famously efficient 'dabba' delivery system of lunchboxes, from homes to offices, connects her to a testy old widower (Irrfan Khan) through notes in the lunchbox.

"It was a very difficult role to cast," said Batra, who after lots of auditions spread over several months, settled on Nimrat Kaur, a relatively unknown actress who had earlier appeared in a couple of TV commercials in India.

For the lead character of Saajan and his office colleague Shaikh, "I always had Irrfan and Nawazuddin Siddique in mind and I was thrilled when they came on board," he said.

Batra has no immediate plans for a new film. With "The Lunchbox" set to release in US then in Hong Kong, Israel, UK, Japan, and Australia "I have a lot of commitments to the film for the next few months - lots of travelling."