Marinate the pork belly with the rice wine and the ground black pepper for about 15 mins.
Cook the kimchi in a skillet until soft. (Alternatively, you can do this directly in the pot where you’ll make the jjigae, but only if the pot is large enough to maneuver easily.)
Place the marinated meat at the bottom of the pot. Add all the other ingredients—kimchi, onion, mushrooms, tofu, water, and the base sauce—into the pot, except for the green onion. (I used a clay pot with a capacity of just over 1 liter. I’ve also successfully made this using an 18cm (7-inch) Staub Cocotte without needing the skillet mentioned in the previous step.)
Bring the pot to a boil over medium-high heat. Once boiling, lower the heat to medium and continue cooking until the meat is completely cooked through, which should take about 10 to 15 minutes from the start of this step. To ensure the sauce is evenly incorporated, gently stir it into the soup using a spoon. Occasionally, spoon some of the broth over the other ingredients to help distribute the flavors. When the meat is done, add the green onion, give it a final gentle mix, and turn off the heat.