Ingredients

• 1 , 6 pound
• 2 tablespoons prepared horseradish
• 2 tablespoons Dijon mustard
• 2 teaspoons kosher salt
• 2 teaspoons coarsely ground black pepper
• 2 teaspoons dried thyme
• 2 teaspoons garlic powder
• 2 stalks celery , cut into 2-inch pieces
• 1 carrot , cut into 2-inch pieces
• 1 small unpeeled onion , quartered and separated

Instructions

1. 1 Gather all ingredients.
2. 2 The day before you plan to serve the prime rib, remove roast from the package and dry thoroughly with paper towels. Set roast on a baking sheet, and place in refrigerator overnight. Remove from refrigerator 1 hour before cooking to allow beef to reach room temperature.
3. 3 Rub the roast all over with horseradish and Dijon mustard. Mix kosher salt, black pepper, thyme, and garlic powder together in small bowl; sprinkle over the roast.
4. 4 Preheat the oven to 450 degrees F (230 degrees C). Place celery, carrot, and onion into the bottom of a roasting pan; place the roast on top.
5. 5 Roast in the preheated oven for 30 minutes. Reduce oven temperature to 350 degrees F (175 degrees C), and roast until the meat is browned and an instant-read meat thermometer inserted into the thickest part of the roast reads 130 degrees F (54 degrees C) for medium-rare.
6. 6 Remove from oven, transfer roast to a platter, and cover with a tent of aluminum foil. Allow to rest for 30 minutes. The temperature of the meat will rise about 10 degrees during resting time.
7. 7 To make au jus sauce: Skim excess fat from pan drippings in the roasting pan. Place the pan over a burner set to medium heat; stir in beef base and 1 1/2 cups of water. Bring to a boil, scraping and dissolving any brown flavor bits from the bottom of the pan.
8. 8 Strain out and discard vegetables. Combine cornstarch and 1 teaspoon of water in a small bowl; whisk the mixture into sauce.
9. 9 Allow sauce to thicken slightly; pour into a gravy boat and serve with roast.
10. 10 Serve and enjoy!

Nutrition per serving