For the butter: Combine the butter and thyme in a food processor and process until smooth, then season with salt and pepper. Scrape the butter into a ramekin, cover with plastic wrap and refrigerate until cold and the flavors meld, at least 2 hours and up to 48 hours.
For the prime rib: Remove the prime rib from the refrigerator 2 hours before roasting. Pat the surface dry with paper towels. Make 8 small slits over the surface of the fat cap and fill each slit with a whole garlic clove.
Place the roast on a large cutting board, then brush with oil and season heavily with salt and pepper 15 minutes before roasting.
Preheat the oven to 450 degrees F.
Place the roast, bone-side down (fat-side up), in a large roasting pan fitted with a rack. Roast for 20 minutes. Reduce the heat to 350 degrees F and continue roasting until a digital instant-read thermometer inserted into the center and ends of the meat registers 125 degrees F for medium-rare doneness, about 3 hours. Start checking the temperature after 2 hours.
Transfer the meat to a cutting board with a juice groove. Pour off all but a few tablespoons of the fat from the pan, and place the roasting pan over two burners set to high heat. Add the shallots and the remaining 3 cloves chopped garlic, and cook until soft, about 4 minutes. Add the wine and vinegar and cook until reduced by three-quarters, about 5 minutes. Add the stock and peppercorns, and bring to a boil. Cook until reduced by half, about 10 minutes. Strain the sauce into a medium saucepan set over low heat. Bring to a simmer and cook until reduced a bit further. Slowly whisk in the cold thyme butter and cook until the sauce thickens (do not boil or the sauce will break). Season with salt and pepper. Finish with a dash of Cabernet Sauvignon vinegar and the chopped parsley to serve.
Have the butcher trim some of the excess fat from the roast, leaving a layer of fat to protect and baste the roast as it cooks.