Mix together potatoes, two tablespoons cornflour, green chilli, salt and pepper powder in a bowl. Shape into small rolls. Heat sufficient oil in a kadai and deep fry the rolls, on medium heat, till golden brown in colour.
Drain on absorbent paper. Heat two tablespoons oil in a non stick pan. Add garlic and sauté till golden brown. Add tomato ketchup, soy sauce and sauté for one minute. Add half cup vegetable stock and allow to boil.
Dissolve remaining cornflour in one fourth cup vegetable stock and add to the sauce. Once the sauce thickens, add fried potato rolls and mix well. Add vinegar and take the pan off the heat.
Serve hot garnished with spring onion greens.