Rosemary-and-Pepper Standing Rib Roast with Two-Mushroom Pan Sauce

Preparation Place rib roast, fat side up, in heavy roasting pan. Mix 4 teaspoons crushed rosemary, salt, and pepper in small bowl. Stir in 1/2 cup oil. Rub mixture all over roast. DO AHEAD Can be made 1 day ahead. Cover and chill. Let stand at room temperature 45 minutes before roasting. Combine 2 cups boiling water and porcini; let soak until mushrooms soften, about 20 minutes. Strain soaking liquid through fine strainer set over measuring cup; reserve porcini. If needed, add enough water to soaking liquid to measure 1 cup. Coarsely chop porcini. Melt 2 tablespoons butter with remaining 2 tablespoons oil in large skillet over medium-high heat. Add fresh mushrooms; sauté until browned, about 6 minutes. Add porcini and garlic; stir 1 minute. Remove from heat. Combine flour, remaining 2 tablespoons butter, and remaining 2 1/2 teaspoons crushed rosemary in small bowl; mash with fork to smooth paste. DO AHEAD Porcini soaking liquid, mushroom mixture, and flour-butter mixture can be made 1 day ahead. Cover separately; chill. Place rack in bottom third of oven and preheat to 350°F. Cook roast until instant-read thermometer inserted straight down into top center of roast registers 125°F to 130°F for medium-rare, about 2 hours 30 minutes. Transfer roast to platter; cover loosely with foil and let rest 35 to 40 minutes. Skim any fat from top of pan juices (there will be a small amount of pan drippings); reserve juices in pan. Set roasting pan atop 2 burners over medium-high heat. Add reserved 1 cup porcini soaking liquid, broth, and wine; bring to boil, scraping up any browned bits. Add mushroom mixture, then butter-flour mixture; whisk constantly over medium-high heat until sauce thickens, about 2 minutes. Season sauce to taste with salt and pepper. Garnish roast on platter with fresh rosemary sprigs. Slice roast and serve, passing mushroom sauce separately.

Preparation Place rib roast, fat side up, in heavy roasting pan. Mix 4 teaspoons crushed rosemary, salt, and pepper in small bowl. Stir in 1/2 cup oil. Rub mixture all over roast. DO AHEAD Can be made 1 day ahead. Cover and chill. Let stand at room temperature 45 minutes before roasting. Combine 2 cups boiling water and porcini; let soak until mushrooms soften, about 20 minutes. Strain soaking liquid through fine strainer set over measuring cup; reserve porcini. If needed, add enough water to soaking liquid to measure 1 cup. Coarsely chop porcini. Melt 2 tablespoons butter with remaining 2 tablespoons oil in large skillet over medium-high heat. Add fresh mushrooms; sauté until browned, about 6 minutes. Add porcini and garlic; stir 1 minute. Remove from heat. Combine flour, remaining 2 tablespoons butter, and remaining 2 1/2 teaspoons crushed rosemary in small bowl; mash with fork to smooth paste. DO AHEAD Porcini soaking liquid, mushroom mixture, and flour-butter mixture can be made 1 day ahead. Cover separately; chill. Place rack in bottom third of oven and preheat to 350°F. Cook roast until instant-read thermometer inserted straight down into top center of roast registers 125°F to 130°F for medium-rare, about 2 hours 30 minutes. Transfer roast to platter; cover loosely with foil and let rest 35 to 40 minutes. Skim any fat from top of pan juices (there will be a small amount of pan drippings); reserve juices in pan. Set roasting pan atop 2 burners over medium-high heat. Add reserved 1 cup porcini soaking liquid, broth, and wine; bring to boil, scraping up any browned bits. Add mushroom mixture, then butter-flour mixture; whisk constantly over medium-high heat until sauce thickens, about 2 minutes. Season sauce to taste with salt and pepper. Garnish roast on platter with fresh rosemary sprigs. Slice roast and serve, passing mushroom sauce separately.