Rub the Prime Rib Roast roast with half of the Dijon, and then sprinkle generously with salt, and half of the peppercorns. Roast in a 275 degree oven until it reached an internal temperature of 110 degrees for rare, 120 degrees for medium rare, and 130 degrees for medium. Remove from oven and cover with foil and let rest 30 minutes. While rib roast is resting, pour off the liquid from cooking the roast, separate out the fat from the juice, and add 3 tablespoons fat to a hot sauté pan. Sauté shallots until just tender, and then deglaze the pan with the brandy. Add the remaining liquid from the roast, and reduce by half. Add the cream, remainder of the Dijon, and remainder of the peppercorns. Taste and season accordingly with salt. Slice Prime Rib Roast , and serve with the au poivre sauce.