In a vessel, fry onions in oil until they turn brown. Once they turn brown, add garlic-ginger paste, and cumin seeds; fry for further few seconds. Now add red chilli powder, turmeric powder, salt and half of garam masala. Stir for 2 seconds and then add meat and allow it to cook in its own water on slow flame. This will take about an hour. Meanwhile, peel potatoes, cut in cubes and soak in water. When meat water dries add tomatoes,and then leave them to soften on medium flame in their own water. Once tomatoes are tender and the water has dried, add potatoes and green chillies and allow to cook potatoes by adding 1 cup of water. Once the potatoes are done and oil starts separating add 1-2 cups of water for the gravy. You can keep the consistency of the gravy according to your desire. Let the gravy cook for atleast 3-5 minutes with lid closed on medium heat.