Heat the oil in a pan. Add the whole garam masala let them sizzle and become aromatic.
Add the chopped onion, and fry for 8- 10 minutes, until golden brown. Add the lamb pieces, and fry for 3- 4 minutes or until the mutton pieces are seared all over.
Add the garlic and ginger paste to the mutton, stir well and then reduce the heat, and let it cook for 3- 4 minutes.
Add the coriander powder, cumin powder, red chili powder, fennel seeds powder, garam masala, tomato, yogurt, and salt, to taste.
Cover the pan with a lid, and then reduce the heat to low, and simmer for 10 – 12 minutes, or until the masala is dry.
Add 1/2 cup of boiling water to the masala, let it cook for another 7 to 8 minutes.
Add enough boiling water to almost cover the mutton, and bring the mixture to a boil, cover the lid and let it cook till 2 whistles then reduce the heat to a simmer, and cook for 8 to 10 minutes, or until the mutton is tender.
Add chopped coriander leaves and serve hot with roti aur rice.