One 5- to 6-pound prime rib roast
Flaky sea salt
Freshly ground black pepper
2 ounces dried porcini mushrooms
1½ cups beef broth, heated
6 tablespoons unsalted butter, cut into tablespoons
7 sprigs fresh thyme, leaves picked and stems discarded
10 large shallots, quartered
6 garlic cloves, smashed
3 bay leaves
1 tablespoon extra-virgin olive oil
1 tablespoon unsalted butter
1 garlic clove, finely chopped
1 pound cremini mushrooms, thinly sliced
¾ cup brandy
¾ cup beef stock
1 tablespoon fresh lemon juice
1 tablespoon finely chopped fresh flat-leaf parsley
Salt and freshly ground black pepper
1. Make the prime rib: Preheat the oven to 500°. Season the prime rib roast with sea salt and pepper and set aside at room temperature for 45 minutes.
2. In a medium bowl, add the dried porcini. Pour the hot beef broth over the porcini and set aside for 20 minutes. Remove the porcini and set aside. Pour the broth through a paper coffee filter or paper towel-lined sieve. Reserve the broth.
3. In a small bowl, combine the butter and three-quarters of the thyme leaves and mix until well combined. Rub 6 tablespoons of the butter evenly over the roast and set aside.
4. In a large roasting pan, combine the shallots, garlic cloves, bay leaves, rehydrated porcini and the remaining thyme. Dot with the remaining thyme-butter and place the roast on top of the mixture.
5. Place the roasting pan in the oven and roast until the top of the meat is browned, about 15 to 20 minutes. Lower the heat to 325° and roast, basting the prime rib every 30 minutes with the pan drippings, until a thermometer inserted in the center of the roast registers 125° to 130° for medium-rare, about 1 to 1½ hours. Remove the roast from the oven, transfer to a cutting board and carefully cover with aluminum foil. Set aside to rest for at least 20 minutes. Separate most of the fat from the pan juices. Reserve the vegetables and pan juices, discarding the bay leaves and any burnt pieces.
6. Make the mushroom sauce: In a large skillet set over medium heat, warm the olive oil and butter until the butter is melted. Stir in the garlic and cook until softened, about 3 minutes. Add the cremini mushrooms and cook, without stirring, until the mushrooms darken and the liquid from the mushrooms begins to evaporate, about 10 minutes. Add the brandy and boil until reduced by half, about 4 minutes. Stir in the reserved vegetables and pan juices. Cook until the liquid has reduced by half, about 5 minutes. Stir in the beef stock and reserved porcini soaking liquid and boil until the liquid is reduced by half, 5 to 7 minutes. Whisk in the lemon juice and parsley, season with salt and pepper and keep warm.
7. Remove the aluminum foil from the roast and carve into slices. Serve the roast warm with the brandied-mushroom sauce.