Combine the cornflour in 1/2 cup of water, mix well and keep aside.
Heat the oil in a wok on high flame.
Add the potatoes and cook on a high flame for a few minutes till they are cooked, while stirring continuously. Remove and keep aside.
In the same oil addbthe garlic, ginger and green chillies and saute on a high flame for a few seconds.
Add the potatoes, tomato ketchup, soya sauce, chilli sauce and salt, toss well and saute on a high flame for another minute.
Add the cornflour mixture and cook on a high flamr for another 2 more minutes or till the mixture thickens and coats the potatoes well. Serve hot garnished with spring onion greens.