Cut pork into thin slices of 0.5cm thickness and flatten lightly. Alternatively, place a piece of plastic on top of slices of pork and pound lightly with meat tenderizer.
Marinade pork with sugar, salt, pepper, starch and both soy sauces in a bowl. Leave for 15 to 30 minutes.
Heat cooking oil and deep-fry potatoes slices till slightly browned, about 5 minutes.
Heat cooking oil in a wok over high heat. Toss in garlic and fry till fragrant. Add pork and stir fry for about 2 minutes till the pork tender but firm.
Add water and simmer for the sauce to slightly thicken. Lower heat, add potatoes and leek. Cook till everything is mixed well.
Serve warm with steamed rice