Prime Rib Roast with Red-Wine Sauce

Ingredients

• 0.8 teaspoon pepper black
• 4  peppercorns black
• 1  carrots finely chopped
• 1 rib celery finely chopped
• 0.7 cup veal demi-glace 
• 0.5 oz porcini mushrooms dried
• 2 sprigs flat-leaf parsley fresh
• 1 sprig thyme leaves fresh
• 2  garlic cloves smashed
• 1 tablespoon kosher salt 
• 2 small onions unpeeled peeled halved lengthwise chopped (1 left and , and 1 and )
• 1 rib prime rib roast with ribs (sometimes called standing rib roast; 9 to 10 lb)
• 0.5 teaspoon salt 
• 0.7 cup shallots chopped ( 3 large)
• 1 tablespoon tomato paste 
• 1  turkish or 
• 6 tablespoons butter unsalted
• 2 cups boiling-hot water 
• 750 ml wine such as a côtes du rhône dry red

Equipment

• bowl
• sauce pan
• oven
• whisk
• sieve
• roasting pan
• kitchen thermometer

Directions

1. Let roast stand at room temperature 1 hour.
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.
3. 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.
4. Transfer to a large platter and let stand, uncovered, 30 minutes. (Internal temperature of meat will rise to 130°F for medium-rare.)
5. 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.
6. 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.
7. 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.
8. Pour through a fine-mesh sieve set into another 2-quart heavy saucepan, pressing on and then discarding solids.
9. While wine reduces, soak porcini in boiling-hot water (2 cups) in a bowl until softened, about 20 minutes.
10. 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.
11. 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.
12. Slice roast across the grain and serve with sauce on the side.
13. ·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.