Cut chicken and potatoes into bite-sized pieces.
Slice green onion and onion as well.
Heat cooking oil in a pan and stir-fry the chicken.
When the chicken is partially cooked, add potatoes and onion, and stir-fry together.
Season with soy sauce, sugar, and minced garlic.
Pour in 200ml of water and boil until the potatoes are cooked.
Add green onion at the end and simmer for another 2-3 minutes.
Sprinkle pepper to taste before serving.