India, May 21 -- It began with a packet of toffees and a shared laugh at the foot of the Colosseum. By the time the video finished its journey across social media platforms on Tuesday evening, it had nudged a penny stock in Mumbai by 5 percent, set off a national debate about Indian confectionery on the world stage, and given one of the country's most beloved candy brands an unexpected dispatch to global headlines.

Prime Minister Narendra Modi, wrapping up the final leg of a five-nation European tour that had taken him through the United Arab Emirates, the Netherlands, Sweden, and Norway, arrived in Rome on May 19 at the personal invitation of Italian Prime Minister Giorgia Meloni. What followed was a visit dense with diplomatic signific...