Soak the dals in two cups of water for one hour. Drain and pressure-cook with three cups of water till soft.
Heat the ghee in a thick-bottomed kadai; add the onion and sauté till light brown.
Stir in the chilli powder and turmeric powder.
Add the cooked dals and salt to taste. Mash lightly with the back of a ladle.
Continue to cook, stirring continuously, for two or three minutes.
Heat the white butter in a separate kadai; add the paanch phoron, tomatoes, yogurt and garam masala powder and sauté over medium heat till the fat separates.
Add the mixture to the dals and simmer, stirring occasionally, for two or three minutes. Serve hot, garnished with coriander leaves.