Thoroughly wash the lamb trotters in warm water. If not pre-singed, roast them gently over an open flame to remove any residual hair.
In a large heavy-bottomed pot or pressure cooker, heat ghee over medium heat. Add the sliced onions and fry until golden brown.
Stir in the ginger garlic paste and sauté for 2 to 3 minutes until the raw aroma disappears.
Add the chopped tomatoes, red chili powder, coriander powder, turmeric powder, and salt. Cook until the oil separates from the masala.
Add the lamb trotters to the pot and mix well, coating the meat thoroughly in the masala. Sauté for 5 to 7 minutes until the trotters slightly change color.
Pour in the water and bring to a boil. If using a pressure cooker, cook for 60 to 90 minutes on low heat. If using a standard pot, cover and simmer on low for 3 to 4 hours until the meat is tender and the broth is gelatinous.
Once the trotters are cooked, sprinkle garam masala and slit green chilies over the curry. Simmer for an additional 5 minutes.
Garnish with fresh chopped cilantro and serve hot with naan, roti, or steamed rice.