Blend biriyani spice blend ingredients in a small bowl.

Make ginger-garlic-nut puree by combining onion, garlic, ginger, cashews, and chile in a food processor and pureeing to a paste.

Coat the bottom of a 12-inch saute pan with oil and heat over medium heat.

Stir in the ginger-garlic-nut paste and saute, stirring and scraping up brown bits for about 18 minutes until dark golden brown and aromatic. Adjust heat as needed.

Scrape the paste from the pan, adding water to collect all the glaze and browned bits.

Set the paste aside or refrigerate for up to 2 days.

Place a 12-inch saute pan over medium-high heat, coat with oil, and add sliced onions with salt and pepper.

Saute the onions until golden with dark, crisp edges, about 6 minutes.

Push the onions to the edges of the pan and spread out the lamb in the center.

Reduce the heat to medium and sear the lamb on all sides, letting the liquid cook away. Adjust the heat so the onions don't burn.

Once the meat is seared, stir in the spice blend and cook until aromatic, about 3 minutes.

Add the yogurt to the lamb, 1/2 cup at a time, simmering each addition for 2 minutes, or until it disappears into the saute.

Stir in the tomatoes, the ginger puree, and enough water to barely cover the meat.

Adjust the heat so the sauce simmers very slowly and cook, uncovered, for 1 to 1 1/2 hours, or until the meat is tender and the sauce is reduced and rich tasting.

Rinse the rice in several changes of water until the water is clear, then soak the rice in enough water to cover (with 1 tablespoon of the salt added) for 30 minutes to 6 hours. Drain.

Lightly toast the saffron for 30 seconds to 1 minute in a small, dry saucepan over medium heat. Immediately add the milk.

Pull the pan from the heat and set aside to steep for a minimum of 20 minutes.

Fill a 6-quart pot two thirds full of water. Add the remaining 3 tablespoons salt and bring the water to a boil.

Drop in the rice and cook it like pasta for about 5 minutes, or until it's tender but with a slight firmness.

Drain in a sieve immediately and spread the rice out on a towel or cookie sheet so it cools quickly.

Take the lamb out of the refrigerator and preheat the oven to 325°F.

Butter the inside of a shallow 3- to 3 1/2-quart baking dish.

Mound the lamb in the center and cover it with the rice, patting it with a spatula into a smooth dome.

Drizzle the rice with the saffron milk.

Tent foil over the dome so that it does not touch the rice. Seal it around the edges of the dish, then bake the biriyani for 45 minutes to 1 hour, or until it is hot at its center.

While the biriyani bakes, prepare several layers of paper towels on a baking sheet next to the stove.

In a 10-inch skillet over medium-high heat, warm the oil and butter and fry the onion until crisp.

Lift the onion out with a slotted spoon, spread on the paper towels, and sprinkle with salt to taste.

In the same oil, fry the raisins until they puff, and scoop them out onto the towels.

Briefly fry the nuts until golden, then cool them on the towels.

To serve the biriyani, remove it from the oven, lift off the foil, and scatter the garnishes over the top.

Serve it hot, making sure each helping has some of the garnishes. Pass a yogurt raita along with the biriyani.