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

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.