In a mortar and pestle grind the peppercorns, garlic, chili flakes and ginger together and mix in the salt and pepper. Coat the Chateaubriand evenly with the mixture and let sit at room temperature for twenty minutes. In a heavy bottomed pan, heat the peanut oil to almost smoking. Quickly add the sesame oil and swirl to combine, then add the roast and sear on all sides. Place the pan in a hot (400 degree oven) and roast for 20 minutes or until an internal read thermometer registers 155 degrees. Remove the roast from the oven and the pan and let rest for ten to fifteen minutes. Slice and serve.