Preheat your oven to 415 F.
Clean and trim the lamb shanks. Any thin pieces of extra fat or tendons can be trimmed away but leave the majority of the fat as it is necessary for roasting.
Place the lamb shanks in a roasting pan and season both sides well with all the spices, salt, and pepper.
Drizzle some olive oil on them and rub everything in.
Roast uncovered for about 20 minutes to give them some color.
Remove from the oven and lower the temperature to 325 F. Add the rosemary, onions, and garlic to the roasting pan and cover well with 2 layers of aluminum foil.
Return the pan to the oven and let the lamb slow roast for 1 ½ to 2 hours. The longer they roast, the more tender they will be.
Once they have cooked to your desired doneness, let them rest for about 10 minutes before serving.
Optional: Collect the juices from the pan and place in a fat separator. If you don't have one, pour into a heatproof container and let cool until the fat has risen to the top and skim it off. The remaining juices can be used to pour over the lamb while serving. Serve in a flat platter and garnish with the roasted rosemary, garlic, and onions. Enjoy!
