Start with the night before serving. Trim any excess fat from the leg of lamb and make slits in the fat pad on top of the roast, spaced one and a half inches apart. This allows the garlic and seasoning to penetrate the meat, enhancing flavor.
Rub the entire roast generously with kosher salt, ensuring some salt gets into the slits. This step is crucial as it seasons the meat deeply.
Sprinkle the roast with freshly ground black pepper to add a touch of spice that balances the sweetness of the glaze.
Cover the lamb with plastic wrap and refrigerate overnight. This helps the flavors develop and tenderizes the meat.
On the day of roasting, remove the lamb from the refrigerator an hour before cooking. This allows it to reach room temperature, ensuring even cooking.
Insert the garlic slivers and rosemary pieces into the slits made earlier. This step infuses the lamb with aromatic flavors.
Preheat your oven to 425 degrees Fahrenheit. The high initial temperature helps to sear the meat, locking in juices.
Roast the lamb in the preheated oven for 20 minutes. You’re aiming for a nice crust to form on the outside.
After 20 minutes, reduce the oven temperature to 300 degrees Fahrenheit. This lower temperature will allow the lamb to cook slowly and evenly.
Brush the exposed parts of the roast with orange marmalade. This sweet glaze caramelizes as it cooks, creating a beautiful finish.
Baste the lamb with more marmalade approximately every 20 minutes. This keeps the meat moist and enhances the glaze.
Continue roasting until a meat thermometer inserted into the center reads 125 degrees Fahrenheit for rare. This should take about another hour, depending on your oven.
Once cooked, remove the lamb from the oven and cover it with foil. Allow it to rest for 20 to 30 minutes before carving. Resting is essential as it helps the juices redistribute throughout the meat.
After resting, carve the lamb and serve with your favorite sides. Enjoy the fruits of your labor!