Add ½ tbsp oil in a pot, add onion, garlic and ginger, fry for 1 minute under medium heat
Add chicken, keep stirring until meat is no longer pink in colour, about 4 minutes
Add in cubed potatoes, fry for about 1 minute
Add 3 tbsp dark soy sauce, fry for another 5 minutes
Add water to cover the meat and potatoes, turn to high heat. When boil, turn heat to low and simmer for 15 minutes
Add in the cornflour mixture and keep stirring until gravy thickens