Peel the calf’s liver, removing the thin menbrane. Cut into even 3 cm (1¼ inch) cubes.
For the marinade, combine the olive oil with the rosemary, balsamic vinegar and pepper berries or peppercorns, add the liver to this mixture and chill for 1 hour.
Thread the liver onto skewers and season. Cook over high heat for 5–6 minutes, turning the skewers regularly.