1. Prepare your grille, and bring the coals up to medium high. You really should use good quality, premium hardwood lump charcoal for this – not the petroleum briquets that are cheap, but nowhere near the real wood flavor that you want for authenticity – not to mention your health. Ideally your grill allows for the meat to be positioned quite close to the coals, because you are going for a charred surface on your meat.
2. Liberally apply the rock salt all over your steak. Do not rub it in, that will make the meat too salty, but slather it on well, and don’t worry about any salt that falls off.
3. Grill the steak about 5 minutes on each side if you like medium rare, a little less for rare, a little more for well done. Turn the steaks over only once.
4. When your meat is cooked, use a large grilling spatula or large broad knife and remove the extra salt by slapping it against the fillets. Do this on both sides, the let the meat to rest for 2-3 minutes before carving it.

For the Chimichurri-

1. 

Place the chopped parsley and cilantro in a large mixing bowl, then add in all the other ingredients.
2. Stir everything together thoroughly.