Dice the onion, pork, and potato into small cubes.
Heat some cooking oil in a pan and stir-fry the pork.
Add the onion, potato, and zucchini and stir-fry together.
Add the black bean paste (chunjang) and stir-fry over low heat.
Pour in water and add sugar, then bring to a boil.
Once the potatoes are cooked, add starch water to adjust the consistency.
Pour the jajang sauce over the cooked noodles.