The “Top Chef” folks are officially in town filming their Boston-based 12th season. Host Padma Lakshmi posted an Instagram of herself Friday with Kristen Kish (far left), Boston’s own Season 10 winner. And on Sunday, locals tweeted that they were at a food fest thrown by the Bravo series. “I thought I was going to a food festival but nope I guess I’ll be on bravo’s Top Chef,” tweeted @MISSVLLISON. “Top Chef” will film around Boston through June and will air its next season in the fall.