1. Marinate the Chicken:
* In a large bowl, combine all the marinade ingredients: gochujang, gochugaru, soy sauce, mirin, sugar, sesame oil, minced garlic, minced ginger, and black pepper. Mix well until a smooth paste forms.
* Add the cut chicken thigh pieces to the marinade. Using your hands (preferably gloved, as gochujang can stain) or a spoon, toss the chicken thoroughly to ensure every piece is well-coated.
* Cover the bowl and let the chicken marinate in the refrigerator for at least 30 minutes. For deeper flavor, marinate for 2-4 hours, or even overnight.

2. Prepare the Vegetables and Rice Cakes:
* While the chicken is marinating, prepare all your vegetables: peel and slice the sweet potato, chop the cabbage, slice the onion, and cut the scallions. Keep the tougher white/light green parts of the scallions separate from the tender dark green tops.
* If using tteok (rice cakes), ensure they are softened by soaking in warm water and then drained. If they are fresh and soft, you can skip the soaking.

3. Cooking the Dakgalbi:
* Use a large, wide, heavy-bottomed pan or skillet (a 12-inch cast iron skillet, a large non-stick frying pan, or an electric skillet works well). Dakgalbi is traditionally cooked in a large pan that allows ingredients to spread out.
* Heat 1 tablespoon of cooking oil in the pan over medium-high heat.
* Add the marinated chicken to the hot pan in a single layer, if possible. Cook for 3-4 minutes per side, until it starts to brown and char slightly. Don’t move it around too much initially to allow for good caramelization.
* Add the sliced sweet potatoes and the white/light green parts of the scallions. Stir everything together and cook for about 5-7 minutes, stirring occasionally, until the sweet potatoes begin to soften. The chicken will continue to cook.
* Add the chopped cabbage and sliced onions to the pan. It might seem like a lot of cabbage, but it will wilt down significantly. Stir well to combine with the chicken and sauce. Cook for another 5-8 minutes, stirring frequently, until the cabbage is tender-crisp and the chicken is cooked through. If the mixture looks too dry, you can add a tablespoon or two of water or chicken broth.
* Add the drained tteok (rice cakes) and the dark green parts of the scallions. Stir and cook for another 3-5 minutes, or until the rice cakes are soft and chewy and have absorbed some of the sauce.
* If using perilla leaves, stir them in during the last minute of cooking. They wilt quickly and add a wonderful aroma.

4. Optional Cheese Finish:
* If adding cheese, reduce the heat to low. Make a space in the center of the pan or sprinkle the mozzarella cheese evenly over the top of the Dakgalbi.
* Cover the pan with a lid (or foil if your pan doesn’t have one) and let it cook for 2-3 minutes, or until the cheese is completely melted and gooey.

5. The Grand Finale: Dakgalbi Fried Rice (Bokkeumbap)
* This is an essential part of the Dakgalbi experience! Once most of the chicken and vegetables have been eaten, leave some of the leftover sauce and a few small bits of chicken/vegetables in the pan.
* Add 1-2 cups of cooked short-grain rice to the pan.
* Drizzle with a little extra sesame oil.
* Add some chopped kimchi (squeeze out excess liquid) and crumbled gim (seaweed snacks) or shredded nori.
* Using a spatula or sturdy spoon, mix everything vigorously, scraping up any browned bits from the bottom of the pan. Flatten the rice mixture into a pancake shape.
* Cook for a few minutes until the bottom is slightly crispy. Some like to crack an egg into it as well.
* Serve the fried rice straight from the pan.