Combine 259 g whisked yogurt with salt to taste in a roomy bowl. Stir in 1000 g lamb pieces until fully coated, cover, and place in the fridge to marinate for about 1½ hours.
Set a large, heavy pot over medium heat and warm 150 g ghee or vegetable oil. Toss in the whole spices for the oil and fry for just a few seconds until fragrant.
Add 100 g finely chopped onion and sauté for 5 to 7 minutes until deep golden brown. Stir in the spices and pastes for the sauce, 100 g chopped tomato, and salt to taste; cook for about 5 minutes, breaking down the tomatoes until the moisture boils off and the mixture turns pulpy.
Tumble in the marinated lamb along with all the yogurt from the bowl. Fry for 2 to 3 minutes until the oil begins to separate from the gravy base.
Stir in 750 ml water and bring close to a boil. Turn the heat down to medium-low, cover with a tight-fitting lid, and let it simmer for 1 to 1½ hours until the lamb is fork-tender.
Take off the lid, raise the heat, and boil off the excess liquid until almost no thin sauce remains and a rich masala coats the meat. Strew 11–13.2 g chopped coriander leaf over the top to serve.
Use about a third of the weight (0.5 g ground for a 2.5 cm piece), stirred in with the ground spices rather than fried whole, since the powder burns quickly.
Use 80% of the weight, finely shredded and browned slowly with a pinch of asafoetida. Replicates the bulk and natural sweetness in gravies without allium.
Steep a tiny pinch (0.1 g per 2 g turmeric) in 2 tbsp warm water; use to match the rich golden hue. Contributes an aristocratic, honeyed floral flavour rather than earthy bitterness.
Use 50% of the weight mixed with equal parts ground coriander and a pinch of ground cinnamon, ground cloves, and ground green cardamom. Sprinkle near the end for a warming finish.
Use 40% to 50% of the fresh tomato weight mixed with a splash of water. Imparts a deeper red colour, thicker sauce, and slightly sweeter cooked flavour.