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