Wash and soak chana dal, moong dal and rice in four cups of water for three to four hours. Drain and grind to a coarse paste. Remove stems, wash and chop green chillies finely. Peel, wash and grate ginger. Wash curry leaves and pat them dry. Add chopped green chilliest, grated ginger and salt to the ground paste and shape them into lemon-sized balls.
Heat sufficient oil in a kadai and fry them till crisp and brown. Drain onto an absorbent paper and keep aside. Wash and pressure-cook toovar dal in three cups of water with turmeric powder and salt. When cooked blend the dal in a liquidizer. Keep aside. Remove stems of whole red chillies and grind them along with coconut, cumin seeds and urad dal to a fine paste.
Keep aside. Heat two tablespoons of oil in a vessel and season with mustard seeds and curry leaves. When the seeds crackle add asafoetida and the coconut paste. Fry for three to four minutes. Add the blended dal and add four cups of water to reach the required consistency. Simmer on low heat for some time. Just before serving add the vadais to the dal and serve hot.