Spiced lamb with ginger and cilantro

Spiced lamb with ginger and cilantro

2 large bunches fresh cilantro
1 6'' piece fresh ginger (about 5 ounces)
1 leg of lamb (4 1/2 pounds), butt half, bone in

1. Up to 1 day before you plan to serve, remove the leaves from 1 bunch of the cilantro and put them in a food processor.
2. Using a small, sharp knife, peel the ginger. Cut the ginger into large chunks and add to the food processor with the cilantro. Add 1 teaspoon coarse salt and 1/2 teaspoon cracked black pepper. Process until a course paste forms. (Do not overprocess because you donýt want the result to be watery.)
3. Rub the ginger-cilantro mixture over the lamb. Tightly pack some on top of the lamb to form a thick layer. Place the lamb in a large plastic bag and secure it tightly. Refrigerate for 8 hours.
4. Remove the lamb from the refrigerator and let it sit at room temperature for 30 minutes before cooking. Meanwhile, preheat the oven to 375 degrees F.
5. Using a sharp knife, lightly score the top of the lamb with lines 1'' apart. Place the lamb in a heavy, shallow roasting pan and roast for about 18 minutes per pound, or until the temperature on an instant-read thermometer reaches 145 degrees F for medium-rare. You may need to drain the fat halfway through cooking. Transfer the lamb to a cutting board, let it rest for 5 minutes, and carve it as desired.
6. Serve immediately, garnished with fresh cilantro sprigs from the remaining 1 bunch cilantro.