Mix the cornflour 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 chillies, ginger and garlic.
Fry for a minute. Add the potatoes.
Add sauces, salt and sugar.
Stir well and add the cornflour solution.
Cook till the wateriness is gone.
Add spring onions and stir. Serve hot.