Soak the broken wheat for three or four hours in two cups of water. Soak the dhuli urad dal, chana dal and moong dal in one cup of water.
Marinate the mutton with the yogurt and salt for one hour, preferably in a refrigerator. Heat the oil in a kadai and deep-fry the onion slices till golden.
Drain on absorbent paper. Place the soaked broken wheat, urad dal, chana dal and moong dal in a pressure cooker.
Add the marinated mutton, green chilli paste, ginger-garlic paste, shahi jeera, peppercorns and turmeric powder and mix.
Stir in the mutton stock. Add the salt, mint leaves, garam masala powder and half the fried onions. Seal the cooker with the lid and cook for thirty to forty minutes.
Remove the lid when the pressure is reduced completely and remove the mutton with a slotted spoon. Purée the rest of the mixture in a blender.
Put the mutton back into the mixture. Heat the ghee in a pan. Pour the khichda into it and bring to a boil.
Lower heat and simmer for ten minutes. Adjust the consistency by adding milk.
Serve, garnished with the remaining fried onions, sprigs of mint and lemon wedges.