Preheat oven to 475°F. Put roast, ribs side down, in center of a 13- by 9-inch flameproof roasting pan and rub all over with 1/2 tablespoon oil. Cut about 1/2 inch from tops of garlic heads to expose cloves and discard tops. Rub beef all over with cut sides of garlic and sprinkle with 2 tablespoons thyme, pressing to adhere. Season beef generously with salt and pepper. Put garlic heads on a double layer of foil and drizzle with remaining 1/2 tablespoon oil. Wrap garlic tightly in foil. Roast beef in middle of oven 30 minutes. Remove beef from oven and with a bulb baster skim all but about 1/2 cup fat from pan. Baste beef with fat remaining in pan. Reduce temperature to 375°F. Add garlic to oven. Roast beef, with garlic, 1 1/4 to 1 1/2 hours more, or until a meat thermometer inserted into center of meat registers 115°F. Transfer garlic in foil to a rack and transfer beef to a platter, reserving pan juices. Let beef stand 25 minutes. (Meat will continue to cook, reaching about 130°F. for medium-rare.) While beef is standing, remove all but about 2 tablespoons fat from pan. Add shallot to pan and on top of stove cook over moderate heat, stirring, 2 minutes. Unwrap garlic. Protecting your hand with a doubled paper towel, squeeze roasted garlic into shallot mixture and discard skins. Add vinegar, wine, bay leaf, and remaining tablespoon thyme and boil mixture, scraping up brown bits and mashing garlic with a wooden spatula against bottom of pan, until reduced to about 1/2 cup, about 5 minutes. If using demiglace, stir into garlic mixture and boil sauce until reduced to about 2 cups, about 5 minutes. Whisk in butter. If using beef broth, in a small bowl mash together butter and flour to make a beurre manié [See how to make beurre manié on streaming video]. Stir beef broth into garlic mixture and boil sauce until reduced to about 2 cups. Whisk beurre manié into broth mixture and cook over moderate heat, whisking, until sauce is smooth and slightly thickened, about 3 minutes. Pour sauce through a fine sieve into a bowl, pressing hard on solids. Season sauce with salt and pepper. Cut rib roast into slices and serve with sauce. (Go to tips on carving a rib roast.) Serves 8. Gourmet December 1998 Gerald Barron ( [email protected] ) from Maui Hawaii on 02/07/04 I add a little touch. I combined thime, salt and pepper with flower. Slivered garlic and inserted then into the roast. Then browned the roast in a very hot roasting pan, then roasted at 200 to a internal temp of 120. Most important letting it rest for 30 minutes. A Cook from Delta, British Columbia, Canada on 12/27/03 This was the first roast that Ive made and it turned out fabulously. I followed advice from Spicer, CO by starting it off at 500 first, then lowered to 250 and slow cooked it. Our guests and my family really enjoyed it. so tender that my one-yr-old had no trouble eating it with less than half of his teeth in yet! Thanks for the great advice. A Cook from Calgary on 11/24/03 This is an elegant, delcious change from typical brown gravy. Have made it twice using plain ol beef stock and dried thyme, and it turned out fabulous both times. We are a small family, and cook small roasts. I do the 400 for 25 minutes then 250 for the rest of the time method, and it works nicely, even with cheaper cuts of meat. This recipe is a keeper.