Heat the oil in a large pan and add the curry leaves to it. Throw in the onions, green chillies ginger and garlic to it as well.
Once the onions have softened, add all the spices to it (turmeric, coriander powder, cumin powder, black pepper and garam masala). Sauté well till the raw smell of turmeric goes away.
Add the tomatoes to the pan and sauté till they are soft. Now add the mutton pieces to the pan along with the salt. Sauté well till the color of the meat changes on the outside evenly
Now add some water to just cover the meat in the pan. Cover and cook on medium high heat for a while till the meat is cooked well and almost falls off the bone.
Once the water evaporates, take off the cover and increase the heat a little and sauté again so that it thickens up a little. Check seasoning and add some more black pepper for more heat or more salt if needed.
Switch off heat and garnish with chopped cilantro. Serve with plain steamed white rice or rotis.