Yesterday was the Full Moon Festival in Korea and it is customary to crack nuts. They can be walnuts, peanuts, chestnuts- any nuts that make that distinct crackling, snap sound.
Why do Koreans do this? It is believed that the sound will scare away evil omens and allow the good spirits to entire your house.
The family I visited also usually eat Korean Fried Honey Cakes. I seriously need to stay away from these because they are SOOOOO good (and I don't think they are all that healthy.