Soak dal for 1 to 2 hours. Rinse and grind it coarsely along with the red chillies ,salt and asfoetida. The batter should be too watery and its consistency should be thick enough to spread on the leaf. Now, rinse and dry the leaf before use. Spread the dal-batter on the leaf. Roll the leaf carefully without breaking. Tie a string around each roll and steam cook the rolls for 5 mins. After steam cooking the rolls , cut them into 1 inch length pieces. Heat the oil in a pan or kadai and put mustard seeds to splutter. Add the chopped onions and fry till golden brown and then fry the steam cooked cabbage parrupu curry along with it for 2- 3 mins. This cabbage paruppu curry can be served hot with rice or chapathis.