Ingredients

BUTTER
½ cup (1 stick) unsalted butter, softened
1 tablespoon finely chopped fresh Italian parsley leaves
2 teaspoons finely chopped fresh mint leaves
2 large garlic cloves, minced
½ teaspoon kosher salt
¼ teaspoon freshly ground black pepper

MARINADE
⅔ cup extra-virgin olive oil
½ cup finely chopped fresh Italian parsley leaves and tender stems
⅓ cup fresh lemon juice
1½ tablespoons kosher salt
1½ tablespoons paprika
2 teaspoons ground cardamom
4 garlic cloves, finely chopped
1½ teaspoons ground cumin
1½ teaspoons ground ginger
1½ teaspoons ground turmeric
1 boneless leg of lamb, about 5 pounds, butterflied and trimmed of excess fat

Directions

Combine the butter ingredients. Set aside.

Whisk the marinade ingredients. Reserve and set aside one-half of the marinade to use for basting the lamb on the grill. Pour the remaining marinade into a large, resealable plastic bag. Place the lamb inside the bag, press the air out, and seal tightly. Turn the bag to distribute the marinade, place in a bowl, and refrigerate for 2 to 4 hours, turning occasionally. Remove the lamb from the bag and discard the marinade. Allow the lamb to stand at room temperature for 15 to 30 minutes before grilling.

Prepare the grill for direct and indirect cooking over medium heat (350° to 450°F).

Grill the lamb, fat side down, over direct medium heat, with the lid closed, until nicely marked, 10 to 12 minutes. Turn the lamb over and grill for 5 minutes more, basting the lamb with the reserved marinade. Then move the lamb over indirect medium heat and grill, fat side up, with the lid closed, until an instant-read thermometer inserted into the thickest part of the lamb registers 125° to 130°F for medium rare, 20 to 30 minutes more, basting occasionally with the reserved marinade. Remove from the grill and let rest for 5 to 10 minutes.

Cut the lamb across the grain into thin slices. Melt the herb butter, and then drizzle it over the lamb. Serve right away.