1 Prime rib roast (4-10lbs)
3 tablespoons coarse sea salt
4 tablespoons fresh ground black pepper
1/2 tablespoon dry thyme
1 large onion (quartered)
4 cloves of garlic
4 carrots (halved)
2 stalks celery (halved)
4 mushrooms (whole)
4 sprigs of fresh thyme
1 can beef broth (14.5 oz)
1. Rinse the roast and pat it dry a paper towel.
2. Rub top of the roast with olive oil. Do not apply rub to the bottom of the roast, because the rub will dissolve in the beef broth that is added to pan and make it too salty.
3. Add salt, pepper and thyme in a bowl and mix.
4. Sprinkle the rub over the top of the roast.
5. Wrap the roast in clear plastic wrap.
6. Refrigerate overnight.
7. Heat the grill to 500F (260C).
8. Sear the top and bottom of the roast for 3 minutes each side, then remove it from the grill and wrap it in aluminum foil.
9. Fully close the top vent and draft door of the grill until the temperature reaches 325F (163C).
10. Add 3-4 palm size wood chunks to charcoal.
11. Insert the heat deflector with the plate in the bottom position. Insert the cooking grate.
12. Open the top vent and draft door to maintain the temperature.
13. Place the roast in a roasting pan. Add beef broth to the bottom of the pan. Add the onion, garlic, carrots, celery, mushrooms and sprigs of fresh thyme around the roast (optional). The vegetables and herbs act as aromatics and enhance the flavor of the au jus.
14. Cook the prime rib roast until the desired internal temperature is reached.
15. Remove the roast from the pan and place it on a cutting board. Allow it to rest uncovered for 15 minutes before carving.
16. Pour the drippings from the pan into a large bowl and spoon off any fat that rises to the top. Serve the au jus in small bowls with each serving of prime rib.
17. Carve the prime rib in 1/2″ thick slices and serve with au jus and horseradish sauce.