If there was ever a show-stopper to end all show-stoppers for roasts, this would undoubtedly be the one. A 6 to 7 pound roast (with 3 bones) will easily feed up to 8 guests. The homemade au jus and creamy horseradish sauce put it over the top. Don't be intimidated by this roast...follow these steps and you'll have a perfectly cooked prime rib that will blow your guests away!
Several hours in advance of roasting, or even better, the night beroe, liberally salt and pepper the roast all over. Place on a roasting rack in a roasting pan and place in the refrigerator, uncovered.
Two hours before roasting, remove the roast from the refrigerator and place it on the counter.
Meanwhile, use a fork to mix together the softened butter, rosemary, thyme, and garlic in a small bowl. Set aside.
Preheat oven to 250°F.
Rub the butter/herb mixture all over the roast. Pour the beef broth into the bottom of the roasting pan. Place the roast (in the pan on the rack) in the oven (uncovered) and roast until an instant-read thermometer reaches 125°F for medium-rare or 130°F for medium. (The roast will continue cooking as it rests, it typically will increase another 5 degrees).
Remove the roast from the oven and loosely tent with foil for at least 30 minutes, or up to 1½ hours.
Make the Creamy Horseradish Sauce
While the roast is in the oven, or even better, 1 or 2 days in advance: In a medium-sized bowl, mix together all of the ingredients of the creamy horseradish sauce until fully incorporated. Transfer to a jar or container with an air-tight lid and place in the refrigerator until ready to serve.
Make the Au Jus
After the roast has come out of the oven for the initial cooking, add the wine and Worcestershire sauce in a medium saucepan over medium-high heat. Place a sieve over the saucepan and pour in the drippings from the roasting pan (you'll need to carefully remove the roast from the pan to do this. Add the roast back to the roasting rack after pouring the drippings).
Simmer the wine mixture until slightly reduced, about 4 to 5 minutes. Add the beef broth and cook on high for another 10 to 15 minutes until reduced by about a third. The sauce will still be thin, but slightly thickened. Season with a pinch of salt.
Pour into a fat separator, or skim the grease from the top of the liquid, and then transfer it into a serving vessel.
Finish the Roast and Serve
Turn the oven to the highest setting, 500°F or 550°F.
Place the roast (in the roasting pan) back into the oven and cook until darkened and crispy on the outside, about 6 to 8 minutes.
Remove from the oven. If the roast is held together with string, use kitchen shears to cut them away and remove the bones. If the bones are attached to the roast, run a sharp knife down the side of the roast, between the bones and the meat, until the bones fall away.
Use a carving knife to slice the roast into ¼-inch or ½-inch slices. Serve at once with au jus and creamy horseradish sauce passed at the table.
If you go with a boneless prime rib roast, follow the recipe as is, and remove the roast from the oven when an internal temperature reaches 125°F for medium-rare or 130°F for medium. Prime cuts of prime rib can be found at many well-stocked butchers or ordered online. Chuck grade of prime rib is still extremely delicious, and less expensive. No need to cover the roast while cooking in the oven for the low-temp cooking or the high-temp sear. When you remove the roast from the low-temperature oven, be sure to allow it to rest for at least 30 minutes or up to 1½ hours. Tent with foil. The roast will continue to cook and increase approx. 5 more degrees.You can ask your butcher to cut the bones away for you, and then have them tied back into place with kitchen twine. Or, you can use a large, sharp knife to cut the bones away from roast after the high-temperature searing. If desired, you can leave the bones and cut the roast into large chops. Each chop will have about 2 lbs of meat and would serve at least 2 people. (We recommend removing the bones and slicing). The horseradish sauce can be made up to 2 days in advance. In fact, the sauce gets better after sitting in an air-tight container in the fridge for at least 24 hours. If you prefer, you can make the au just sauce directly in the roasting pan. Simply place the pan on the stove over medium heat. Follow the recipe as written, straining the sauce before serving.