Cut the onion, pork, potato, and carrot into bite-sized pieces.
Heat cooking oil in a pan and stir-fry the pork.
Add the onion, potato, and carrot, and stir-fry together.
Add the chunjang (black bean paste) and stir-fry with the ingredients.
Pour in water and sugar, and bring to a boil.
Adjust the thickness with starch water.
Pour the finished jajang sauce into a bowl.