Cut the king oyster mushrooms and onion into bite-sized pieces.
Heat oil in a pan and sauté the onion.
Add the king oyster mushrooms and stir-fry together.
Make the seasoning sauce by mixing gochujang, soy sauce, red pepper powder, minced garlic, and water.
Add the seasoning sauce and rice cakes to the pan and simmer.
Once the ingredients are cooked well, transfer to a plate to finish.