In a large bowl, mix together the gochugaru, gochujang, soy sauce, vegetable oil, sesame oil, rice syrup, chilies, garlic, ginger, and salt and pepper to form a thick paste.
Add the chicken and mix to coat each piece of chicken. Cover and refrigerate at least 1 hour.
Heat a large oven proof pan (cast iron pan) to medium heat. Add the chicken with the marinade, and water or chicken stock.
Cover and simmer for 10 minutes, or until the chicken is cooked through. The marinade/sauce should reduce a bit. Remove lid.
Set oven to BROIL.
Top the chicken with shredded mozzarella cheese and broil for 2-3 minutes, or until the cheese is melted to your preference and begins to brown.
Remove, garnish, and serve!