Japchae is a curious mix of slippery and crunchy. The glass noodles are coated with the meat and vegetable juice and oil that makes it easy to the throat (but pretty hard with the steel chopsticks that Koreans usually use). The vegetables and the meat give it texture variation that perfectly harmonizes with the dangmyeon (the noodles).
Japchae is simply translated as stir-fried noodles with vegetables but once upon a time in the Korean royal court a certain Yi Chung was promoted to a high government position because he earned the favor of the King to whom the first known japchae was served. Back in the day this was a royal dish, but nowadays this is a permanent banchan (side dish). You’ll find many Korean fast food chains overseas serving a small portion of japchae along with rice and chicken pops. As this is an easy-to-make and a filling dish, it is also popular with big group celebrations.
The additional ingredients that usually pop up in japchae instructional include a variety of mushrooms, and then carrots, onions and spinach. These are all stir-fried separately before getting mixed in.