Heat oil in a pan and add urad dal to it. Now add chopped tomatoes green chilli and onion to it and saute it. After cooling grind it in a fine paste. Heat oil in a pan and add mustard seeds and curry leaves to it. Pour this tadka on chutney. For dosa heat, a tawa and grease it with oil. Pour fermented dosa batter to it and spread it quickly on tawa. Sprinkle some oil and cook it. Now keep stuffing in the middle and fold it. Yummy crispy dosa is ready to serve.