Trim the fat cap of your roast if it's more than ¼ inch thick. Tie the roast between the bones with butcher's twine.

In a small bowl, mix the mustard, Worcestershire sauce, rosemary, thyme and garlic.

Apply the mixture to the meat and season it generously with salt and pepper. Let it sit uncovered in the refrigerator for 8 hours.

Preheat your smoker to 250°F (121°C) Place the prime rib inside the smoker and smoke it for about 4 hours or until the internal temperature reaches 125°F (52°C) for rare or 135°F (57°C) for medium-rare. Use hickory bisquettes for this recipe.

Remove the meat from the smoker and loosely tent it with foil. Let it rest for 30 minutes.

Use a sharp knife to carve the meat. Serve with horseradish, if desired.