Japchae is a Korean stir-fry dish. The key to japchae is using cellophane noodles made from sweet potato starch. Cellophane noodles can be made from different starches, such as mung bean, but are all called glass noodles because they are translucent when cooked. Versions of japchae (like this one) are simple to prepare and can be customized with different sautéed veggies or by adding meat.