Put mutton, oil, onion, and red chilies in pan, mix garam masala in yogurt and pour over meat mixture. Cook (uncovered) on high heat for about 10 minutes. Add salt, ilaichi and garlic paste. Seal the pan and lid with flour (if not using pressure cooker), and cook on very low heat for 45 minutes. If water has not dried, cook on high heat till it does and only thick gravy is left. Do not stir hard. Serve garnished with coriander.