1) Preheat oven to 150 degrees C.
2) Add oil to saute pan. Season meat on all sides with salt and pepper. Sear meat on all sides, about 2 to 3 minutes each side. Place meat on sheet tray with a rack. Roast meat for 30 to 40 minutes. Crank oven up to 230 degrees C and roast for an additional 15 to 20 minutes until crust forms and meat is nicely colored. When done, allow to rest before slicing. In a small bowl reserve juice for bourbon mushroom sauce.
3) In a large saucepan over medium-high heat, add 70 g butter. Add garlic, mushrooms and onion and cook for 4 to 5 minutes until nicely Add flour and mix well to form pasty roux.