Active Time

　　1 hr

　　Total Time

　　3 3/4 hr

　　Big and beefy, this luscious cut of meat definitely has a celebratory presence. Here it partners with porcini mushrooms, which are both rubbed on the roast and incorporated into the sauce. For the best flavor, look for well-marbled meat.

　　

Ingredients

Makes 8 servings

　　

For roast

1 (4-rib) prime rib roast with ribs (sometimes called standing rib roast; 9 to 10 lb)

　　1/2 oz (2 tablespoons) dried porcini mushrooms, ground to a powder in a blender

　　1 tablespoon kosher salt

　　3/4 teaspoon black pepper

　　

For sauce

2 small onions (1 left unpeeled and halved lengthwise, and 1 peeled and chopped)

　　3/4 stick (6 tablespoons) unsalted butter

　　2/3 cup chopped shallots (about 3 large)

　　1 carrot, finely chopped

　　1 celery rib, finely chopped

　　2 garlic cloves, smashed

　　1 tablespoon tomato paste

　　2 sprigs fresh flat-leaf parsley

　　1 sprig fresh thyme

　　1 Turkish or 1/2 California bay leaf

　　4 black peppercorns

　　1 (750-ml) bottle dry red wine such as a good-quality Côtes du Rhône

　　1/2 oz dried porcini mushrooms

　　2 cups boiling-hot water

　　2/3 cup veal demi-glace

　　1/2 teaspoon salt

　　

Special Equipment

an instant-read thermometer

　　

Cook roast:

Step 1

Let roast stand at room temperature 1 hour.

　　

Step 2

Put oven rack in middle position and preheat oven to 450°F. Trim all but a thin layer of fat from roast, then rub roast all over with porcini powder, salt, and pepper. Transfer to a rack set in a 13- by 9-inch roasting pan. Roast beef 20 minutes, then reduce temperature to 350°F and roast until thermometer inserted into center of meat registers 110°F, 1 1/2 to 2 hours more. Transfer to a large platter and let stand, uncovered, 30 minutes. (Internal temperature of meat will rise to 130°F for medium-rare.)

　　

Prepare sauce while meat comes to room temperature and roasts:

Step 3

Cook halved onion, cut sides down, undisturbed, in 1 tablespoon butter in a 2-quart heavy nonreactive saucepan over moderate heat until browned well, about 4 minutes. Add chopped onion, shallots, carrot, celery, garlic, and 2 tablespoons butter and reduce heat to moderately low, then cook, covered, stirring occasionally, until chopped vegetables are softened, 8 to 10 minutes. Add tomato paste, herbs, bay leaf, peppercorns, and 2 cups wine and boil, uncovered, over moderately high heat until liquid is reduced to about 1/4 cup, 25 to 30 minutes. Pour through a fine-mesh sieve set into another 2-quart heavy saucepan, pressing on and then discarding solids.

　　

Step 4

While wine reduces, soak porcini in boiling-hot water (2 cups) in a bowl until softened, about 20 minutes. Drain porcini in a paper-towel-lined sieve set over a bowl and reserve soaking liquid. Rinse porcini and pat dry, then finely chop. Set aside.

　　

Step 5

Add porcini-soaking liquid, demi-glace, and remaining 1 3/4 cups wine to reduced liquid in saucepan and boil, uncovered, over moderately high heat, skimming off froth occasionally, until reduced to about 2 cups, 20 to 35 minutes. Stir in reserved porcini, then reduce heat to low and whisk in 1/2 teaspoon salt, any juices from meat accumulated on platter, and remaining 3 tablespoons butter until incorporated.

　　

Step 6

Slice roast across the grain and serve with sauce on the side.

　　Cooks' notes:

　　·Sauce can be made 2 days ahead and cooled completely, uncovered, then chilled, covered. Reheat before using.

　　·Stainless steel, glass, and enameled cast iron are nonreactive; avoid pure aluminum and uncoated iron, which can impart an unpleasant taste and color to recipes with acidic ingredients.