Japchae is one of, if not THE most popular noodle dish in Korea. Also known as chapchae, it's made from sweet potato starch noodles (called dangmyeon), which are stir-fried with vegetables, soy sauce, sugar and sesame oil. Most recipes for japchae will call for beef (or even leftover bulgogi), but I prefer to leave mine vegetarian. In addition to being a good vegetarian meal, since the dangmyeon are gluten-free, japchae is a healthy meal for those with gluten sensitivity.
Japchae is typically served as a side dish or on a bed of rice (bap), but I find it filling enough for an entire meal. The only ingredient that might be difficult to find are the noodles; here in Birmingham, I am able to buy dangmyeon at most of our Asian markets. However, if you cannot find these noodles, you can substitute cellophane noodles (maifun/saifun), which can be found in the Asian section of most grocery stores (I've even seen cellophane noodles at Wal-Mart).
This is a great, healthy recipe that takes under 15 minutes to make. The measurements are only a suggestion; feel free to substitute different vegetables, or add meat, tofu, kimchi or even omelet strips. Actual cooking time is only around 5 minutes; the hardest part of this recipe is the vegetable prep.