Boil the buckwheat noodles in boiling water and rinse in cold water.
Cut the onion, zucchini, and pork into bite-sized pieces.
Add cooking oil to a pan and stir-fry the pork.
Add the onion and zucchini and stir-fry together.
Add the jajang (black bean) sauce and mix well with the ingredients while stir-frying.
Add water and starch water to adjust the consistency.
Pour the finished jajang sauce over the cooked buckwheat noodles.