In a medium bowl, combine the lamb cubes, whisked yogurt, ginger paste, garlic paste, Kashmiri red chili powder, coriander powder, and salt. Cover and let marinate at room temperature for 30 minutes while you prepare the other ingredients.

Heat ghee or oil in your heavy-bottomed pot over medium heat. Add the thinly sliced onions. Fry, stirring frequently, until they turn an even, golden-brown color (about 12 to 15 minutes). Do not let them burn. Use a slotted spoon to transfer them to a plate lined with paper towels. Spread them out so they cool and crisp.

Once the fried onions are cool and crisp, crush them with your hands or grind them in a small food processor into a coarse paste with 1 tablespoon of water if needed. Set aside. Drain the soaked cashews and blend them with 2 tablespoons of fresh water to form a smooth, thick paste. Set aside.

In the same pot with the remaining ghee, lower the heat slightly. Add the green cardamom, black cardamom, cloves, cinnamon, and bay leaf. Let them sizzle for 30 seconds until aromatic. Add the marinated lamb with all its marinade. Increase heat to medium-high and sear the lamb, stirring constantly, until the moisture from the yogurt dries up slightly and the oil begins to separate at the edges (about 8 to 10 minutes).

Add 1/2 cup of warm water and the ground mace. Stir well, scraping the bottom of the pot. Bring to a gentle boil, then turn the heat to low. Cover the pot tightly with a lid and simmer until the lamb is tender (about 45 to 50 minutes). Stir occasionally to ensure the meat does not stick.

Stir in the prepared crushed fried onions and the cashew paste. Mix thoroughly. Simmer uncovered on low heat for 10 minutes. The gravy will thicken and take on a rich, slightly grainy appearance. If it gets too thick, add a few tablespoons of warm water.

Sprinkle the garam masala and drizzle the kewra water if using. Stir gently, cover, and let it rest off the heat for 5 minutes before serving. Garnish with ginger juliennes and serve hot.