I also dry age a prime rib in the fridge for about a week before cooking it and I also serve it with horseradish cream. I will buy a whole root and grate it myself, much better than the store bought jarred stuff. I season it simply, salt and pepper generously applied to the outside just before cooking and a sprig or two of rosemary. I roast it at 325 to rare to medium rare. I like it bloody, my husband prefers it a little more cooked.