Cut onion, pork, potato, zucchini, and cabbage into bite-sized pieces.
Heat cooking oil in a pan and stir-fry the pork.
Once the meat is cooked, add the vegetables and stir-fry together.
Add chunjang (black bean paste) and fry over low heat to enhance the flavor.
Add water and potatoes, then bring to a boil.
Season with soy sauce, sugar, and pepper.
Once the potatoes are cooked, add starch water to thicken the sauce.
Pour the jjajang sauce over boiled noodles to serve.