How to Make It
Combine all the marinade ingredients. Place the legs of lamb in a roasting pan that will hold the meat snugly. With a pastry brush, brush the marinade over all sides of the legs of lamb. Cover with plastic wrap and marinate at room temperature for at least 8 hours.
Preheat the oven to 450 degrees F (230 degrees C).
In a large skillet, heat the peanut oil over high heat. Remove the legs of lamb from the marinade, drain, and sear the lamb on all sides, 2 to 3 minutes per side.
Return the lamb to the roasting pan with the marinade and any bones and reserved trimming.
Place in the center of the oven and roast, allowing 10 to 12 minutes per pound (500 g) for medium rare, 15 minutes for medium. (Lamb is medium rare at an internal temperature of 140 degrees F (60 degrees C), medium to well done at 145 to 175 degrees F (63 to 80 degrees C). Turn the lamb several times during roasting and baste occasionally.
Remove lamb from the oven and season generously with salt and pepper. Transfer the lamb to a platter, and place on an angle against the edge of an overturned plate. Cover loosely with foil. Turn off the oven and place the platter in the oven, with the door open. Let rest a minimum of 10 minutes and up to 30 minutes. The lamb will continue to cook during this resting time.
7. Meanwhile, prepare the sauce: Place the baking dish over moderate heat, scraping up any bits that cling to the bottom. Cook for 2 to 3 minutes, scraping and stirring until the liquid is almost caramelized. Do not let it burn. Spoon off and discard any excess fat. Add several tablespoons cold water to deglaze (hot water will cloud the sauce). Bring to a boil. Reduce the heat to low and simmer until thickened, about 5 minutes.
While the sauce is cooking, carve the lamb and place on a warmed platter.
Strain the sauce through a fine-mesh sieve and pour into a sauce boat. Serve immediately, with the lamb.