Standing Rib Roast with Potatoes and Mushroom Red Wine Jus

Steps

1. Pat rib roast dry and place, fat-side up, on rack in roasting pan. Lightly score fat and season roast all over with 1 teaspoon salt. Let sit at least 30 minutes. Meanwhile, preheat oven to 450°F with a rack in center position.
2. Finely chop 2 tablespoons rosemary. Coarsely crush peppercorns using a mortar and pestle or folded kitchen towel, crushing with a mallet or rolling pin. In a medium bowl, combine chopped rosemary, crushed peppercorns, garlic and oil. Rub rib roast with oil mixture, pressing rosemary and peppercorns to adhere.
3. Add potatoes to roasting pan around roast and season with salt. Place an oven-safe meat thermometer in thickest part of roast, away from bone. Roast 20 minutes. Reduce heat to 350°F. Roast 1½ to 2 hours, flipping potatoes and basting roast frequently with pan juices, until thermometer reaches 130°F for medium-rare or 145°F for medium.
4. Carefully transfer potatoes to a serving bowl and roast to a cutting board. Pour pan juices into a fat separator, reserving ¼ cup of pan drippings. Let roast rest, uncovered, 20 minutes. Cover potatoes with foil to keep warm.
5. Meanwhile, to a dry medium saucepan, add mushrooms and a pinch each of salt and pepper. Let liquid release from mushrooms and cook 5 to 7 minutes, stirring occasionally, until tender and browned. Add bay leaf, 1 sprig rosemary and red wine. Bring to a boil, then reduce to a simmer and cook until the liquid has reduced, 10 to 15 minutes.
6. To saucepan, add broth and pan drippings. Gently simmer on medium-low until the jus has thickened, 20 to 25 minutes. Remove bay leaf and rosemary sprig. Season red wine jus with salt and pepper to taste.
7. Thinly slice the meat and arrange on a large serving platter. Finely chop 1 teaspoon rosemary. Garnish sliced roast with chopped chives and rosemary. Serve with red wine jus and roasted potatoes.