Wash the onions and mushrooms thoroughly and slice them into bite-sized pieces.
Heat cooking oil in a preheated pan.
Add the onions and mushrooms and stir-fry over medium heat.
When the onions and mushrooms turn translucent, add doenjang (soybean paste) and mix well.
Add sesame oil, minced garlic, and red pepper powder, and stir-fry once more.
Once all the ingredients are well-blended, remove from heat.
Transfer the finished ssamjang to a bowl and serve.