Prepare the ingredients: Roughly chop the garlic and slice the onions, mushrooms, and bell peppers. Thinly cut the knuckle steak. Slice the kimchi into one-inch length. Gather the kimchi broth, gochujang, gochugaru, fish sauce, water, and cooking oil.
Sauté the aromatics and steak: Preheat a pot to medium-high temperature. Drizzle the cooking oil and sauté the garlic, onion, and steak for one minute. Then, add the mushrooms and cook for another minute. Stir continuously to avoid burning the ingredients.
Simmer the stew: Add sliced kimchi, kimchi broth, water, gochugaru, gochujang, and fish sauce. Gently stir all the ingredients to mix and cook the kimchi jjigae for twenty-five minutes on medium-high heat with the lid closed. Increase the cooking time to thirty-five minutes using slightly fermented kimchi. Serve immediately with freshly cooked white rice.