1. Mix the two dals and soak in four cups of water for one hour. Drain. Place the soaked dals in a pan with four cups of water, salt to taste, turmeric powder, half the ginger and green chillies.
2. Cover and cook over low heat till the dals are soft. Stir well with a ladle to mix the dals without mashing them.
3. Heat the ghee and butter in a kadai; add the cumin seeds, remaining ginger and green chillies. Stir and add the onion and sauté till light brown. Add the tomatoes and sauté till the tomatoes soften. Add the chilli powder and sauté for half a minute. Add the sautéed spices to the dal and mix well.
4. Simmer for a few minutes and serve hot, garnished with coriander leaves.