Finely chop the chicken breast.
Dice the onion and bell pepper.
In a bowl, combine chicken breast, vegetables, mozzarella cheese, and salt, and mix well.
Knead the hotteok mix with water and roll it out into a 10cm diameter circle.
Place the filling on top of the dough and fold it into a half-moon shape.
Heat oil in a pan and cook over medium-low heat until golden brown.
Cook both sides until crispy, then serve.