Heat 2 tablespoons of oil in a heavy-bottomed pot over medium-high heat. Add the lamb pieces and sear until browned on all sides, about 8 to 10 minutes. Remove the lamb and set aside.

In the same pot, add the remaining oil if needed. Add the chopped onions and cook until golden brown. Stir in the ginger paste and garlic paste, cooking for 1 minute until the raw smell disappears.

Add the coriander powder, turmeric powder, red chili powder, and salt. Stir for 30 seconds, then add the chopped tomatoes. Cook until the oil begins to separate from the tomato mixture, about 5 minutes.

Return the browned lamb to the pot and mix well with the masala. Pour in 240 ml (1 cup) of water, bring to a boil, then cover with a lid, reduce heat to low, and simmer until the lamb is fork-tender, about 40 to 45 minutes, ensuring the internal temperature reaches 74°C / 165°F at the thickest piece.

While the lamb is simmering, blanch the fresh spinach in boiling water for 2 minutes, then transfer immediately to ice water. Drain well and blend into a coarse puree.

Add the spinach puree and ghee to the cooked lamb. Simmer uncovered over medium-low heat for 10 minutes to let the flavors meld. Stir in the garam masala and serve hot.