Mix the corn flour and water. Keep aside. Peel and chop the potatoes into long thick chunks.
Heat oil in a wok or pan, add some potatoes at a time. Fry till light golden brown. Finish all potatoes similarly. Keep aside. Remove half the oil.
In the remaining oil, add the chilies, ginger and garlic. Fry for a minute. Add the potatoes.
Add sauces, salt and sugar. Stir well and add the corn flour solution. Cook till the wateriness is gone.
Add spring onions and stir. Serve hot.