1. Preheat oven to 325°. Place lamb on a rack in a shallow baking pan, fat side up. Season with salt and pepper. Bake, uncovered, 1-3/4 to 2-1/4 hours or until meat reaches desired doneness (for medium-rare, a thermometer should read 135°; medium, 140°; medium-well, 145°).
2.Meanwhile, drain plums, reserving 1/2 cup syrup. In a food processor, place the plums, reserved syrup, garlic, lemon juice, soy sauce, Worcestershire sauce and basil. Cover and process until smooth; set aside half of the plum sauce.
3. Baste lamb every 15 minutes during the last hour of roasting. In a small saucepan, simmer reserved sauce 5 minutes; serve with meat.
