Marinate the chicken. In a medium bowl, add soy sauce, Mirin (sweet cooking wine), honey, and oil. Whisk to combine. Add chicken thighs that have been cut into 2-inch chunks. Mix until the chicken is fully coated. Marinate in the refrigerator for at least 1 hour but preferably overnight.
Cook the chicken. Heat cast iron skillet over medium-high heat. Add about 1 Tbsp of oil to coat the bottom of the pan. Swirl to coat the bottom of the pan. When the oil shimmers, add the chicken. Brown the chicken in batches, one layer at a time, making sure not to crowd the pan. It's ok if the chicken is not fully cooked. Transfer to a clean plate. Repeat process until all the chicken is cooked.
Make the "fire" sauce. In a food processor, add the onion, Asian pear, garlic cloves, gochujang, gochukaru, soy sauce, sugar, scotch bonnet peppers, and sesame oil. Whizz until pureed.
Add "fire sauce" to the chicken. Place all the browned chicken back into the skillet. Add the spicy sauce directly to the chicken in the pan. Mix around with a spatula or wooden spoon until the chicken is completely coated in sauce.
Cook chicken and "fire sauce" together. Reduce heat to medium and simmer until the sauce becomes dark red, thick, and reduced, about 12-15 minutes. The chicken and sauce should bubble somewhat vigorously. Lower heat, if needed. Feel free to add water if the sauce looks too dry (about 1 Tbsp at a time). Keep an eye on the sauce, mixing it from time to time.
Preheat oven. While the chicken cooks, preheat the oven to 350F/176C.
Melt cheese. Remove skillet from heat. Add rice cakes, if using, and scatter over the chicken and fire sauce mixture. Sprinkle the cheese on top of the rice cakes and chicken. Make sure the top of the pan is evenly covered.Place skillet in oven until cheese melts, about 5 minutes. It should be a gentle melting. Watch carefully and make sure it doesn't overcook!
Serve. Remove from oven. Garnish with sliced green onion and sprinkle with sesame seeds, if desired. Serve immediately with rice and enjoy!