These puffy steamed buns — fist-sized and generously stuffed — float through the supermarket’s walk-up window seven days a week. A team of dogged women makes the Korean street-food staple from scratch in three flavors: velvety red bean, zesty kimchi with pork, and a milder mix of juicy pork nubs and shredded veggies. Your first bite releases a fragrant puff of steam, and you’re hooked.