Note: Use meat with or without the ribs; Dave prefers the ribs, but as there are not enough for six people, he saves them for leftovers. The bonus of being the chef, he says, is I get to eat them.
1. Preheat oven to 400 degrees F. Take 1 head of garlic and trip top, so that cloves are exposed. Place garlic, cut side up, on a square of aluminum foil approximately 8 by 8 inches. Brush with 2 tsp. olive oil. Fold up sides of aluminum foil to make a packet, leaving about an inch of space above garlic before crimping edges to make a seal. Place in a small pan or baking dish.
2. Roast garlic at 400 degrees F for 30 minutes, until light brown and soft enough to be pierced with a fork. Set aside to cool, foil packet open, about 30 minutes. Gently squeeze the cloves from the papery skin of the garlic head into a bowl, mash with a fork or spoon, and serve as a spread, or use according to recipe instructions.
5. Remove meat from fridge 20 minutes before cooking to allow it to come closer to room temperature. Place sliced onion on bottom of a high-edged roasting pan. Lower oven to 325 degrees F.
4. When cool enough to touch, squeeze roasted garlic from each clove in a bowl. Discard skins. Mix garlic with remaining olive oil, rosemary, salt, and pepper. (Garlic mixture may be made one day in advance.) Slather garlic mixture all over meat.
5. Place meat fat side up on top of onions in pan.
6. Bake at 325 degrees F for 2 hours, 15 minutes. Test for doneness. Rare meat is ready when an instant-read thermometer reads 140 degrees F. For medium-rare, temperature should be 155 degrees F; well done is 170 degrees F.
7. Remove meat to a cutting board. Let it rest for 10 to 15 minutes, tented with foil. Remove onions to a small bowl. Discard if they are very dark; otherwise, save to serve with the meal. Place roasting pan on stove top and deglaze with wine or broth over low heat, stirring to scrape up any baked on bits from bottom of the pan. Pour pan juices into a small pitcher to serve the roast au jus.
8. To serve, cut strings. If roast was cooked with ribs, remove ribs to save for leftovers. Bring cutting board to the table and carve prime rib to order. Serve onions, pan juices, and horseradish spread on the side. Leftovers may be frozen.
Source: Hannaford fresh Magazine, November - December 2008