Put the whole rib-cap in a vacuum or cryovac bag. Seal and cook in a water bath at 78°C (172°F) for 36 minutes. Chill quickly in iced water. Use a chargrill pan or hot coals in a fire pit to cook the beef on high heat until it begins to char and blacken; this will take approximately 4 minutes on each side. Remove from the heat and leave to rest for at least 30 minutes before slicing.