What if a morning jog could also produce a batch of homemade butter? That playful idea is behind the “Butter run,” an unusual running challenge that has been spreading across TikTok and Instagram in recent weeks. Blending fitness with a kitchen experiment, the trend began in overseas running communities and is now catching the attention of runners in South Korea as well. The concept is simple. Participants pour heavy cream into a small bottle, zip-top bag or sealed container, tuck it into a runn