Wash the bok choy thoroughly and cut it into bite-sized pieces.
Slice the onion and bell pepper into thin strips.
Heat olive oil in a pan and place the tortilla on it.
Spread tomato sauce evenly over the tortilla.
Top with the prepared bok choy, onion, bell pepper, and chicken breast.
Sprinkle mozzarella cheese on top.
Cover with a lid and cook over low heat until the cheese melts.
Cut into bite-sized pieces and serve on a plate.