Heat oven to 220°C. Bring a large pot of salted water to the boil. Remove steaks from the fridge and allow to come to room temperature. Whilst waiting for the water to reach boiling point, cut any large potatoes in half. Plunge the potatoes into the pot of boiling water and as soon as it reaches the boil again, cook for 5 -7 minutes
Drain the potatoes in a colander and leave to dry out in the colander for a few minutes. Whilst waiting for the potatoes to dry out finely chop the rosemary. In an oven proof pan or small roasting pan toss the potatoes with butter and rosemary. Bake in the oven 25 – 30 minutes, or until golden and crispy. Carefully halfway through toss the pan so that they cook evenly
12 – 15 minutes before the potatoes are ready heat a cast iron skillet or heavy based pan over a high heat. Allow the pan to get very hot.
Meanwhile, using a paper towel, pat both sides of the steaks to dry them, which will help develop color. Brush the steaks with garlic oil and sprinkle liberally with sea salt flakes and a good grind of black pepper.
Using tongs gently lower the steaks into the hot pan. Cook for 3 minutes on the first side until browned. Using the tongs turn over and cook for a further 2 minutes, or until desired doneness.
Remove the steaks to a plate to rest for a few minutes until potatoes are done, about 5 minutes.
As soon as the potatoes are done transfer to the plates with awaiting steaks. Sprinkle potatoes with sea salt and eat immediately.