1 (4-5 lb.) leg of lamb, butterflied and trimmed
15 peeled garlic cloves, crushed, or more if desired
2 Tbs. fresh rosemary leaves
1/2 cup olive oil
2 Tbs. kosher salt
1 Tbs. cracked black pepper
1/2 cup Vin Santo or sherry
1/4 cup chopped fresh mint leaves
With a sharp paring knife, make 10 or 12 slits in the fatty side of the lamb and insert a crushed garlic clove and rosemary leaves into each. Place the lamb in a large zip-top bag.
Mix the oil, salt, pepper, wine or sherry, and extra crushed garlic cloves in a small bowl, then pour the mixture into the bag with lamb. Massage the marinade into the meat to coat it evenly. Let marinate for one hour at room temperature or overnight in refrigerator, turning it occasionally to distribute the liquid.
Prepare a hot grill (350-450°F on a gas grill). Bring the lamb to room temperature. Remove the meat from the marinade, drain it well, and pat it dry. Pour the remaining marinade into a small bowl and set aside. Grill the lamb for 10 to 12 minutes, or until well charred, basting it with the reserved marinade. Turn it over and grill the other side for another 10 to 12 minutes, again basting with marinade. The internal temperature should be 150°F for medium-rare. Remove it from the grill and let it rest for about 15 minutes. Carve it into 1/4-inch slices and serve. The lamb will keep for two days in the refrigerator.