Cut the chicken into bite-sized pieces.
Dice the potatoes, carrots, and onions.
Heat cooking oil in a pan and stir-fry the chicken.
When the surface of the chicken is cooked, add the vegetables and stir-fry together.
Add soy sauce, minced garlic, sugar, red pepper flakes, black pepper, and water, then bring to a boil.
Cover and simmer over medium heat for 20 minutes.
When the sauce thickens, add green onions and boil once more.