How to Make It
In a small skillet, toast all of the spices over moderate heat until fragrant. Transfer the spices to a plate to cool completely, then grind to a powder.
In a large nonstick skillet, heat the oil. Add the onions and cook over moderate heat, stirring occasionally, until golden brown, 10 to 12 minutes. Reserve one-third of the onions in a small bowl. Scrape the remaining onions into a large bowl and let cool to room temperature. Add the next 12 ingredients and 1 teaspoon of the garam masala and mix well. Stir in the lamb until evenly coated. Cover and refrigerate for at least 3 hours or overnight.
In a large enameled cast-iron casserole, heat the ghee. Add the lamb mixture and cook over moderate heat, stirring occasionally, until browned, about 8 minutes. Add 1/2 cup of water, cover and cook over moderately low heat until the lamb is tender, about 1 hour and 15 minutes.
In a large saucepan, bring 4 cups of water to a boil. Wrap the peppercorns, cloves, cardamom pods, cinnamon stick, bay leaf, nutmeg and mace in a piece of cheesecloth and tie into a secure bundle. Add to the saucepan along with the oil, salt and caraway; stir in the rice. Bring to a simmer and cook over moderate heat, stirring occasionally, until the rice is cooked three-quarters of the way, 8 to 10 minutes. Drain well, reserving ¼ cup of the cooking liquid. Discard the spice bundle.
In a small saucepan, toast the saffron over moderately low heat, stirring, until fragrant, about 2 minutes. Remove from the heat and stir in the milk.
Preheat the oven to 350°. Drizzle 1 tablespoon of the ghee in a large enameled cast-iron casserole. Spoon half of the lamb mixture into the casserole in an even layer. Spread half of the rice over the lamb. Top with half each of the remaining cooked onions, saffron milk, ghee, cilantro, mint, rose water and garam masala and 2 tablespoons of the reserved rice cooking water. Repeat the layering once more.
In a medium bowl, mix the flour and water until a rough dough forms. On a lightly floured work surface, knead the dough until it is smooth and pliable, about 5 minutes. Gather into a ball and roll out to a 1/8-inch-thick round that’s a few inches larger than your casserole.
Drape the dough over the top of the casserole, pressing to seal it around the edge. Bake the biryani for 20 to 25 minutes, until the dough is golden and the rice is hot. Brush the crust with ghee and let stand for 5 minutes.
Combine all of the ingredients in a bowl and garnish with mint leaves.
Crack off and discard the dough lid and serve the lamb biryani hot, with the cooling raita.