Heat the mustard oil in a heavy-bottomed pot or Dutch oven over high heat until it starts smoking. Turn off the heat and let it cool for 3-4 minutes. This removes the harsh, pungent bite from the oil.
Turn the heat back to medium. Add the lamb pieces (1000g) in a single layer. Sear for 5-7 minutes, turning occasionally, until the edges turn beautifully golden-brown. This traps the savory juices inside.
Push the meat to the side of the pot. Add the black cardamom, green cardamom, cloves, cinnamon, and asafoetida directly into the oil. Sizzle for 30 seconds until they swell and release a warm aroma.
While the meat is sizzling, whisk the Kashmiri red chili powder, fennel powder, and dried ginger powder into your room-temperature yogurt until it forms a smooth, red paste.
Reduce the stove heat to low. Slowly pour the spiced yogurt mixture into the pot while stirring the lamb continuously. Keep stirring for 3-4 minutes until the yogurt blends completely into the oil without curdling.
Add 1 cup of warm water and salt. Bring it to a gentle simmer, cover with a tight-fitting lid, and let it cook on low heat for 75-90 minutes. You will know it is done when the lamb is fork-tender and a brilliant layer of red oil (rogan) floats gracefully to the top.