Combine the balsamic with all the other ingredients up to and including the salt.
Heat the oil in a frying pan. Fry the steaks for approx. 2 mins. on each side, season, remove the pan from the heat, cover and leave to rest for approx. 5 mins. Plate up the lettuce, drizzle with half of the radish chimichurri. Carve the steak into slices, place on top of the lettuce, drizzle with the remainder of the sauce.