If you’re a Blue Line commuter, maybe you’ve spotted a passenger board at the Western stop carrying a small box exuding the heady aroma of basil or vanilla. Maybe you’ve watched as that person withdraws from said box a steaming-hot, palm-size white bun and then makes it disappear in four bites. Maybe you’ve wondered, Where did that come from?

The answer: Sala Pao Shop, a kiosk that opened inside that L station in Bucktown last fall. Named for the steamed buns sold as street food in Thailand, the takeout spot is the brainchild of Jan Purananda, whose father owns Sticky Rice, a popular northern Thai restaurant in North Center.

Purananda and her mom prepare the buns onsite, generously stuffing each with one of six fillings. The barbecued pork bun ($3), packed with lean morsels of sweet char siu, is the top seller, but the more classically Thai-flavored offerings — say, slow-cooked beef in panang curry with coconut milk and makrut lime leaves ($3) — are warmly satisfying. In too much of a hurry for breakfast or a snack? At least snag a milky Thai iced tea ($3) for the road.