Let's cook.
In a large bowl, combine the chicken pieces with soy sauce, sesame oil, gochujang, gochugaru (if using), minced garlic, and minced ginger. Mix well and let marinate for at least 15 minutes at room temperature.
Heat 1 tablespoon of vegetable oil in a large pot or Dutch oven over medium-high heat. Add the marinated chicken and cook for 5-7 minutes, stirring occasionally, until lightly browned on all sides.
Add the sliced onion to the pot and cook for 3-4 minutes until softened.
Pour in the chicken broth and bring the mixture to a boil. Reduce the heat to medium-low, cover, and simmer for 10 minutes.
Add the cubed potatoes to the pot. Stir gently to combine.
Cover again and continue to simmer for another 15-20 minutes, or until the potatoes are tender and the chicken is cooked through.
Taste and adjust seasoning if needed. Serve hot with steamed rice.
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