Heat two tablespoons of oil in a pan; add the green chillies and sauté for half a minute. Add the chicken liver and salt and sauté over high heat for three to four minutes, stirring continuously. Remove from heat and set aside. Heat the remaining oil in a thick-bottomed kadai; add the cumin seeds and when they begin to change colour, add the onions and sauté till golden brown.
Add the ginger and garlic pastes and sauté for one minute. Add the tomatoes and salt, cover and cook over low heat for two to three minutes. Add the red chilli powder, coriander powder and turmeric powder and continue to cook for another minute. Add the minced mutton, sauté for two minutes and stir in half a cup of water.
Cover and cook over medium heat for fifteen to twenty minutes till the mutton is tender, the water has evaporated and the oil separates. Stir in the sautéed liver and garam masala powder, cook for one minute and serve hot, garnished with coriander leaves and lemon wedges.