Japchae (also spelled "chapchae") is a Korean dish that is based on slippery, resilient sweet potato noodles (sometimes mung bean noodles are used, but they have a more tender texture).
Because the gochujang (Korean chilli ... the carrot and potatoes are tender. The sauce should be light but not watery. If necessary, scoop the solids into the serving dish, and simmer the sauce ...