In the same oil, add the garlic, ginger and green chillies and stir fry for a few seconds. Add the potato fingers, tomato ketchup, soya sauce, chilli sauce and salt.
4 large potatoes, 1 teaspoon chopped garlic, 1/2 teaspoon chopped ginger, 1 teaspoon chopped green chillies, 1 teaspoon tomato ketchup, 2 tablespoons soya sauce, 1/2 teaspoon chilli sauce, salt to taste