The first time I tried the Korean Stir-Fried Glass Noodles a.k.a Japchae was when my manager brought the dish in for a potluck a few years ago. It was literally one of The Best things I've tried, made me go back for refills.
Bring water to a boil, add a bit of oil. Add noodles and cook them for 5-6 minutes. Drain when cooked.
Preheat skillet to high heat. Cook the pre-sliced beef until it's golden brown. Season beef with half portions of the following - soy sauce, sesame oil and brown sugar, while it's cooking.
Place noodles in a large bowl, top them with cooked beef.
Dice onion into long strips. Cut carrots into strips and chop green onion. Preheat an oiled skillet and toss in the carrots and onion.
When the veggies soften up, add in the remaining half portions of the following - soy sauce, sesame oil and brown sugar. Add in pressed garlic, green onions and cook for a few minutes until it's softened.
Add diced spinach into the mixture and turn off the heat imminently.
Add all vegetables to the noodles and toss everything together.
Serve while it's still warm. This dish also reheats well.