Heat sufficient oil in a kadai and deep fry the cooked rice till crisp. Drain on absorbent paper and set aside. Heat one tablespoon oil in a non stick pan. Add ginger and sauté for a minute.
Add mushrooms and toss on high heat for three to four minutes. Add bean sprouts and toss. Add five and half cups vegetable stock and allow to boil.
Add soy sauce, salt, black pepper powder and mix well. Dissolve cornflour in the remaining vegetable stock and add this to the soup.
Once the soup thickens, add vinegar and cook for one minute. Serve piping hot garnished with spring onion greens and crisp fried rice.