Ingredients

Prime rib

• 1 ½ tablespoons Szechuan peppercorns
• 1 ½ tablespoons black peppercorns
• 1 ½ tablespoons white peppercorns
• 6 pounds prime rib roast
• Salt
• 1 tablespoon vegetable oil
• 1 stick unsalted butter (cut into tablespoons)
• 6 thyme sprigs
• 4 bay leaves
• 4 marjoram or oregano sprigs
• 5 garlic cloves (smashed)
• 4 large shallots (sliced 1/ inch thick)

Sauce

• 2 ounces dried porcini mushrooms
• 1 ½ cups boiling water
• 2 tablespoons extra-virgin olive oil
• ¾ pound white mushrooms (thinly sliced)
• 2 medium shallots (thinly sliced)
• 2 garlic cloves (smashed)
• 3 thyme sprigs
• 1 cup Armagnac
• ½ cup dry white wine
• 2 cups low-sodium beef broth
• 2 tablespoons cold unsalted butter
• Salt and freshly ground pepper

Directions

Instructions Checklist

• Step 1 Preheat the oven to 325°. In a pepper grinder or a spice mill, coarsely grind all of the peppercorns. Transfer to a small bowl. Season the roast with salt and the pepper mixture.
• Step 2 In a large ovenproof skillet, heat the oil until shimmering. Add the roast, fat side down, and cook over moderate heat until browned, about 5 minutes. Turn the roast and brown it on each of the other sides, about 13 minutes longer. Set the roast, fat side up, in the skillet and add the butter. When the butter is melted, baste the roast all over. Add the thyme, bay leaves and marjoram and roast for 1 hour.
• Step 3 Add the garlic and shallots to the skillet and continue roasting the meat until an instant-read thermometer inserted in the center registers 130° for medium-rare, about 45 minutes longer.
• Step 4 In a heatproof bowl, cover the porcini with the boiling water and let soak until softened, about 20 minutes. In a large skillet, heat the olive oil. Add the white mushrooms, shallots, garlic and thyme and cook over moderately high heat, stirring occasionally, until the mushrooms and shallots are browned, about 8 minutes. Add the Armagnac and wine and boil over moderately high heat until reduced by half, 5 minutes.
• Step 5 Lift the porcini from their soaking liquid; reserve the liquid. Rinse the porcini and cut any large pieces in half. Carefully pour the porcini soaking liquid into the skillet, stopping before you reach the grit at the bottom. Boil the sauce until reduced by three-fourths, about 8 minutes. Add the beef broth and boil until reduced to 1 1/2 cups, about 8 minutes. Strain the sauce through a fine sieve into a small saucepan, pressing on the solids; add the porcini.
• Step 6 When the roast is done, transfer it to a carving board and let rest for 20 minutes. With a slotted spoon, transfer the shallots and garlic to a plate. Bring the sauce to a simmer, remove from the heat and whisk in the butter, 1 tablespoon at a time; season with salt and pepper. Carve the roast into slices. Scatter the shallots and garlic on top and serve with the porcini sauce.

Make Ahead

The porcini sauce can be prepared through Step 5 and refrigerated overnight. Reheat gently and whisk in the butter before serving.

Suggested Pairing

To pair with the complex, buttery sauce for this luxurious meat, consider a spicy, fruity Zinfandel.