1. Remove your prime rib from the refrigerator to the counter, 1 to 1 ½ hours before cooking.
2. Preheat your oven to 450 degrees.
3. With a paring knife, make slits in the beef and insert the garlic clove slices into each slit.
4. Rub the olive oil all over the beef and sprinkle with salt and pepper mixture, pressing into the meat.
5. Place the meat into the oven and cook for 15 minutes. Lower the temperature to 350 degrees and continue to cook approximately another 45-50 minutes. Check temperature with an instant read thermometer. You are looking for 130 degrees in the center. Remove, tent with foil and allow to stand 15 minutes before cutting.
Roasted Shallot Mustard Sauce:
In a wide high sided sauce pan, heat the drippings from the roast pan over medium heat. Add the shallots and lower the heat to medium low. Stirring often, pan roast the shallots for approximately 20 minutes until crispy, being careful not to burn. Lower the heat if they are cooking too fast.
Remove the shallots. Add the port and beef stock and reduce over medium heat for 10 minutes. Add the heavy cream and continue to reduce for another 5 minutes. Add the butter, whisking it into the sauce, then add the mustard, crispy shallots and salt and pepper. Whisk until slightly thick. Remove and add chives.
Remove the bones from the prime rib. Slice into 6 pieces. Pour sauce around the sides of the beef and serve with your favorite potato or vegetable side.