Make 20 small incisions in the lamb in various places and tuck a slice of garlic into each incision.
In a bowl combine the lavender, rosemary, mint and olive oil. Rub the mixture over the lamb and refrigerate for a minimum of 2 hours.
Preheat an outdoor grill or the broiler unit of your range. If you are using the outdoor grill, place the lamb on the grill 4 in. from the coals. If you are using the broiler, place the lamb in a 7- qt. sauteuse and place the pan 4 in. from the broiler element.
Broil or grill until the first side has reached a rich, caramelized color, about 15 minutes.
Turn the lamb and continue to cook until a meat thermometer reads 130°F-135°F or medium rare. Cover with foil and let rest for 15 minutes.
Slice the lamb across the grain, place on a warm platter, garnish with fresh rosemary sprigs and serve.