Preheat the oven to 90°C. Once it’s up to temperature, it’s time to start pan-frying.
Unusually, we cook sirloins directly from the fridge rather than letting them get to room temperature – this can quicken the process but it can also mean the centre of the steak cooks too quickly. Our method ensures an even cook.
Season the steak with salt and put in a pan. Turn the heat to low. Start by cooking the sirloin standing upright, fat side down, to render it. Gradually increase the heat to medium; after about 5 minutes when there is a pool of bubbling fat sufficient to caramelise the steak in, turn the steak onto its side. Turn up the heat. Flip the steak after 2 minutes and cook the other side for an additional 2 minutes. At this point, you may wish to open a window or turn off your fire alarm.
When both sides are nicely browned, add 75g of the butter to the pan. Cook for another 4 minutes on each side. If the butter starts to brown but the steak hasn’t caramelised (you’ll know if the steak has caramelised because the crust of the steak should be nut- brown like a light ale and smell sweet rather than burnt) add another 50g butter.
For the last 30 seconds add the thyme sprig and crushed garlic and then transfer to a baking tray to rest for 5 minutes.
Now probe the centre of the steak with a meat thermometer; it should be just under 20°C. Transfer to the preheated oven and cook for 25 minutes, then remove and probe the centre of the steak again – you are looking for it to be between 48–52°C. It may need a bit longer back in the oven.
Rest for 5 minutes before removing the bone from the meat and slicing. Pour over the resting juices and season with a pinch of sea salt and some freshly ground black pepper.
