Take the steak out of the fridge and let it sit at room temperature 2 hours before cooking.
Preheat the oven to 400 degrees F.
Heat a heavy bottomed skillet over medium-high heat. Rub 1 tablespoon vegetable oil all over the steak and season it with salt and pepper on both sides. Place the steak in the preheated skillet to sear on one side. Sear the face-up side with a blowtorch simultaneously. When both sides of the steak are browned, transfer the skillet into the preheated oven to finish cooking.
Cook the steak until it reaches an internal temperature of 140 degrees F on an instant-read thermometer for medium-rare. Remove the skillet from the oven and transfer the steak to a plate to rest while you make the sauce.
Place the skillet over medium heat and add 2 tablespoons of the butter. Add the onions and mushrooms and saute until all the water released from the mushrooms has evaporated. Pour in the bourbon and beef broth and cook until the liquid has reduced by half. Turn off the heat and add the remaining 2 tablespoons butter. Swirl the butter around in the skillet until it melts and then quickly stir in the cream. Season the sauce, to taste, with salt and pepper. Slice the steak across the grain and pour the hot bourbon sauce over it and serve.