Soft yet hard. It's when you bite into a ssam of oyster and bossam.
Bossam is Korean word for a bundle. You wrap the oyster and sliced meat in a lettuce often with kimchi and ssamjang(sauce for these type of food) and eat it up in one bite.
It has to be my favorite Korean delight.
Jongro has the best Gul(oyster)Bossam places.
Jongro 3Ga station, exit # 15 into narrow endless streets and you will find the whole little town full of GulBossam diners.