I just had the best, and I mean the best steak in my life. Here is what I did:
I took the long hunch fillet steak (fallow) and put it in a food grade bag (the ones you get from the supermarket to keep food in the freezer). In went some cracked steak pepper, sea salt flakes, olive oil, chilli flakes, dried rosemary and dried thyme. I shook the bag so the ingredients mix and cover the meat evenly and left it to marinade for about an hour.
I put the cast iron skillet on and when it was VERY hot I put the steak, 15-20 seconds each side so it is nicely sealed. I then 'butterflyied' the meat and cooked for a further 3 minutes each side.
Try it and you will not regret it. I am SO happy!