Lay a slice of prosciutto flat on a chopping board, taking care not to tear it. Place the lamb stack at one end and roll to encase it. Repeat to create rolled packages. Season each with the second measure of salt and the pepper. Heat the olive oil until simmering in a sauté pan, then add the rolls and seal. Transfer them to an oven dish and cook for 3 minutes on both sides or until an internal temperature of 55°C is reached. Remove from the oven and allow to rest in a warm place for 5 minutes
Braised Lettuce
Discard dark coloured outer leaves from the lettuce and cabbage. Separate the lettuce and 12 of the cabbage leaves and remove the central ribs. Keeping the lettuce and cabbage leaves separate, stack each and slice into long thin strips. In a large saucepan, reduce the chicken stock by half, add the cabbage and cook for 2 minutes. Add the butter, lettuce, peas and minced garlic. Stir to combine and coat with butter, then remove from the heat. This must be served immediately so timing is important. Taste and season.
Assembly
Arrange the drained lettuce and peas in the centre of the plate.Slice the lamb in half on a 45° angle and place on top of the lettuce. Spoon the prune and Armagnac jus on and around the lamb, and drizzle truffle oil over the top.