Preheat the oven to 350°F.

Trim excess fat from the lamb shanks and season generously with salt.

Combine the cinnamon, nutmeg, cardamon, ground dried rosebuds, black pepper and turmeric. Rub the mixture into the lamb shanks. Cover with plastic wrap and let sit at room temperature for 1 hour.

Set a Dutch oven or heavy-bottomed pan over medium heat, add the oil and when it is hot sear half of the lamb shanks. As the shanks brown, remove them to a plate and repeat with the remaining lamb shanks, about 10 minutes.

Discard all but 2 tablespoons of the accumulated fat in the pan and sauté the chopped onion until softened, about 5 minutes.

Pour the chicken broth to the pot and stir in the rosewater, lime juice and the orange zest. Add the bundle of thyme sprigs and the bay leaves.

Place the reserved lamb shanks, and the accumulated juices into the pot, snuggling them down into the braising liquid so that the liquid covers two-thirds of the shanks. Increase the heat to high and bring the pot to a boil. Remove from the heat, cover the pot and transfer to the oven. Braise covered for 1-1/2 to 2 hours until the lamb shanks are tender and beginning to fall off the bone.

Remove the lamb shanks, place on a platter, cover and keep warm.

Strain the braising liquid through a fine-mesh sieve into a saucepan, discarding the thyme, bay leaves and onions.  There will be about 3-4 cups of liquid remaining.  Skim off and discard the fat that rises to the top. 

Bring the braising liquid to a boil then reduce the heat and simmer to reduce to 2 cups.  

Taste the braising liquid adding another teaspoon of rosewater and salt if needed.  Transfer the braising liquid to a pitcher. 

Serve in shallow bowls with a lamb shank on a mound of basmati rice drizzled with the braising liquid and sprinkled with chopped pistachio nuts. Garnish each serving with lime wedges and mint sprigs.