1) Take the steak out of the fridge and let it sit at room temperature for 2 hours before cooking.
2) Preheat the oven to 200C/Gas 6.
3) Heat a heavy-bottomed frying pan over medium-high heat. Rub vegetable oil all over the steak and season it with salt and pepper on both sides. Place the steak in the preheated pan to sear on one side. Sear the face-up side with a blowtorch simultaneously. When both sides of the steak are browned, transfer the pan into the preheated oven to finish cooking.
4) Cook the steak until it reaches an internal temperature of 60C on an instant-read thermometer for medium-rare. Remove the pan from the oven and transfer the steak to a plate to rest while you make the sauce.
Slice the steak across the grain, pour the hot bourbon sauce over it and serve.
1) Place the pan over medium heat and add 30g of butter. Add the onions and mushrooms and saute until all the water released from the mushrooms has evaporated. Pour in the bourbon and beef stock, and cook until the liquid has reduced by half.
2) Turn off the heat and add the remaining butter. Swirl the butter around in the pan until it melts and then quickly stir in the cream. Season the sauce, to taste, with salt and pepper.